Physical Geography Exam 2

Front 1

diabatic processes

Back 1

processes that involve removal or input of heat (energy)

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adiabatic processes

Back 2

processes that do not involve change in heat (energy)

prominent mechanism for the development of clouds and production of rain

Front 3

dry adiabatic cooling

Back 3

as parcel of unsaturated air is moving upward, it expands (P of surrounding air is decreasing) and cools. Sinking parcels experience compression warming

dry adiabatic lapse rate: -5.5 degrees farenheit/1000 ft

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dry adiabatic lapse rate

Back 4

as long as a rising parcel remains unsaturated, the rate of adiabatic cooling or warming remains constant 10 degrees celcius/1000 m

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Remember, as water condenses latent heat is given off. The latent heat given off in an air parcel as condensation takes place, partially offsets the cooling due to adiabatic expansion

Back 5

.

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wet adiabatic lapse rate

Back 6

rate at which a saturated air parcel will cool or warm...it is not constant and varies depending upon the amount of water vapor in an air parcel

avg WALR = 5-6 degrees celcius / 1000 meters

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Environmental lapse rate

Back 7

temperature change of the surrounding atmosphere with height.
It is not a parcel lapse rate. Average ELR = 6.5°C/1000 m

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buoyancy of air

Back 8

The tendency of an object to rise in a fluid

A parcel of air moves vertically until the surrounding air is of equal density (equilibrium level)

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stable

Back 9

Rising air is cooler than surrounding air
Resists vertical movement,
Non-buoyant
Will not move without extra force

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unstable

Back 10

Rising air is warmer than surrounding air
Buoyant
Will rise without external force or will continue to rise even after removing the external force

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conditionally unstable

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Intermediate condition between stability and instability
When an air parcel’s adiabatic lapse rate is between wet and dry rates

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1. Convective Lifting

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Unequal heating of different air surface areas warming one parcel and not the air around it

only spontaneous of the four lifting types

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2. orographic lifting

Back 13

Occurs only when topographic barriers force air to descend upslope and cool to the dew point

Rain shadow area: the area of low rainfall on the
leeward side of a topographic barrier

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3. frontal lifting

Back 14

When unlike air masses meet: air is cooled to the dew point: creation of a zone of discontinuity (front): forces warmer air to rise over cooler air

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4. convergent lifting

Back 15

air parcels converge and the crowding forces uplift

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precipitation formation processes

Back 16

Two mechanisms principally responsible for producing precipitation:

1. Ice crystal formation
2. Collision and Coalescence of water droplets

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ice crystal formation

Back 17

Possible major reason for precipitation outside tropics
-Ice crystals grow faster than the cloud droplets in clouds that contain both
Ice crystals have smaller evaporation rate than cloud droplet.
Air gets saturated more quickly by ice crystals than liquid droplets because crystals have a smaller equilibrium vapor pressure

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collision/coalescence

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Mostly responsible
for precipitation in the tropics
-Rain produced by the collision and coalescing (merging) of water droplets

No ice crystals because cloud temperatures are too warm

Must coalesce enough that the droplets become large enough to fall

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rain

Back 19

The most common and widespread

Drops of liquid water

Result of condensations thawing of ice crystals

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snow

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Solid precipitation in the form of ice crystals, small pellets, or flakes

Formed by direct conversion of water vapor to ice

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sleet

Back 21

Small raindrops freezing during decent

Reach ground as small pellets of ice

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glaze

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Rain that turns to ice the instant it collides with a solid object

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hail

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Rounded or irregular pellets or lumps of ice produced in cumulonimbus clouds as a result of active turbulence and vertical air currents.

Small ice particles grow by collecting moisture from super cooled cloud droplets

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Distribution of Precipitation

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Spatial distribution: most important geographic aspect of atmospheric moisture

Uneven On Earth. However, Some Regularities Evident

Isohyet

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Some Generalizations

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Warmer places have the most precipitation but, not all warm places are “wet”
- Mountain areas “wet”
- Edges of continents are “wet”
- Places with rising air are “wet”
- Coastal regions usually receive more precipitation than interior regions because they are closer to moisture sources
- Due to rising warm trade winds, tropical latitudes contain most of the wettest areas in the world
- The remaining wettest areas are narrow zones along the western coasts of North and South America

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storms

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Temporary and limited as compared to broad scale pressure and wind systems

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air masses and fronts

Back 27

Air masses
Contain uniform temperature and humidity characteristics
Fronts
Boundaries between unlike air masses

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locating fronts

Back 28

Air masses
Contain uniform temperature and humidity characteristics
Fronts
Boundaries between unlike air masses

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Cold Front

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Clouds of vertical development
Short duration, intense precipitation
Steep frontal slope

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Warm Front

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Stratiform clouds
Long duration, light precipitation
Gentle frontal slope
During summer can get storms also

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Stationary Front

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Cloud types depend on the atmospheric stability
Precipitation intensity depends on the situation

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Occluded Front

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Clouds and precipitation depend on the atmospheric stability.

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Atmospheric Disturbances

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Major Disturbances
Midlatitude Cyclones and Anticyclones
Hurricanes
Minor Disturbances
Thunderstorms
Tornadoes

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Midlatitude Cyclones/Extratropical cyclone or wave cyclone

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Migratory low-pressure systemMoves with the westerlies

Responsible for most day to day weather changes

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Jet Streams

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Rossby waves: undulations in the jet stream.

Usually 3 to 6 span globe at one time. Wavelengths 4000-6000 km.

Often takes 10-14 days for a wave to move across US.

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Storm Tracks: North America

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Storms (Storm Tracks) generally travel from West to East in North America all year

They shift north
in summer &
south in winter

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Tropical Weather

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Tropics - region between 23.5° N and S of the equator

amount of solar radiation does not vary much from season to season
winds:
are generally NE, E, or SE (easterly trades)
tend to be quite weak

types of weather systems found in tropics:
Thunderstorms
tropical depressions/storms, and hurricanes

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Easterly Waves

Back 38

Tropical weather is often initiated by easterly waves
easterly waves:
* have wavelengths of about 2500 km
* position is found in a trough of streamline pattern
* convergence/upward motion on east side
* divergence/downward motion on west side
* travel from east to west at 10-20 knots
* hurricanes are often initiated by easterly waves.

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hurricane formation

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1. The surface air that spirals into the center of a low pressure system creates convergence and forces air to rise in the center. This air cools and moisture condenses which releases latent heat into the air.

2. Warm air is less dense than cooler air. The expansion of warm air forces more air outside away from the center of the storm and the surface pressure decreases.

3. When the surface pressure decreases, a larger pressure gradient is formed, and more air converges towards the center of the storm. This creates more surface convergence and causes more warm moist surface air to rise above the surface. This air, as it cools, condenses into clouds. While it does this, it releases even more latent heat.

4. enhance convection - back to 2.

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Vertical cross section of the hurricane circulation

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* at low-levels, air flows cyclonically into the center of the storm.
* diverging, anticyclonic motion at tropopause level
* rising motion occurs in the eyewall, thunderstorms adjacent to the eye.
* subsidence on outer edge of storm
* rain bands
* sinking motion in the eye

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Stages of development

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TROPICAL depression: Winds near the center are constantly between 20 and 34 knots (23 - 39 mph).

tropical storms:Once a has intensified to the point where its maximum sustained winds are between 35-64 knots (39-73 mph), it becomes a tropical storm. It is at this time that it is assigned a name

hurricanes: As surface pressures continue to drop, a becomes a hurricane when sustained wind speeds reach 64 knots (74 mph). A pronounced rotation develops around the central core.

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Ingredients for hurricane formation

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* warm sea-surface temps- greater than 26°C (79°F)
* deep moisture at low levels
* light winds throughout troposphere

* need convergence, a trigger
weak frontal boundary
easterly wave
* typically form between 5°-20° latitude, not on equator.... why? (where all the water isss)
-Effect of landfall
Hurricanes dissipate rapidly at landfall
Remnants may still cause considerable destruction, especially when merging with a midlatitude cyclone

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Hurricane Destruction and Fatalities

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Wind
Heavy rain
Tornadoes
Right front quadrant
Storm surge
Rise in water level associated with pressure drop

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thunderstorms

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Definition: a storm containing lightning and thunder.
Associated with midlatitude cyclones, localized convection, orographic lifting and tropical cyclones.

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Thunderstorms

Back 45

Violent, localized, short lived

Convective storm

Vertical air movement

Thunder and lightening

Due to unstable uplift

Conjunction with other storms (Hurricanes,
Tornadoes and fronts etc.)

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Thunderstorm Formation

Back 46

Ingredients
warm, moist air (often mT)
unstable (or conditionally unstable)
encouraged by diverging air aloft

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Violent Associations w/ thunderstorms

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Hail
Downbursts(Microbursts)
Lightning and thunder
Tornadoes

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Downbursts

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Macrobursts: extreme downdrafts associated with thunderstorms.
Microburst:
smaller
< 5 minute duration
winds up to 146 mph

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Lightning

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Discharge of electricity that occurs
in mature thunderstorms
Cause: charge separation in cloud
sets up electrical potential
Role of lightning is to equalize these differences in
electrical potential.

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Thunder

Back 50

Air poor conductor of electricity
Huge electrical potential develops
Lightning bolt ‘superheats’ the air (30,000C, 54,000 F)
Surrounding air expands violently  sound wave

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Distance from the Thunderstorm

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Speed of light: 300,000,000 km/s
Speed of sound: about 343 meters/s
Distance calculation
for each 3 seconds, 1 km away
for each 5 seconds, 1 mile away

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The Geography of Thunderstorms

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Frequency decreases with distance from equator. Few above 60o
Most occur during summer’s warm temperatures.

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Tornadoes

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Characteristics:

Localized

Cyclonic low pressure cells

Surrounded by a whirling cylinder of wind violently

Partial vacuum develops within the funnel

Have the most extreme pressure gradients

How fast?
No one knows. Estimates: 200 – 500 miles per hour

Usually in warm, moist, unstable air masses in mid
latitude cyclone

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Tornado Formation

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Severe Thunderstorm (1% spawn tornadoes)
Often occur along cold fronts and move to NE
Strong updrafts
Wind shear (change in direction or strength of winds from top to bottom of storm)

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Funnel Cloud

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(a violent, whirling, funnel-shaped cloud that does not touch the ground. Many people mistakenly call these tornados)

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USA tornado geography

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-every state
-tornado alley (Tx, ok, ks, ne)
-most common in us

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Waterspout

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- A tornodo over water - less power- smaller tempgradient

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USA Tornado Season

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Most common when temperature gradient in central U.S. is greatest.

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hydrosphere

Back 59

Describes the waters of the Earth
Water exists on the Earth in stores:
atmosphere, oceans, lakes, rivers, soils, glaciers, and groundwater
Water moves from one store to another:
evaporation, condensation, runoff, precipitation, infiltration and groundwater flow

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avg reservoir residence time

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The residence time of a reservoir within the hydrologic cycle is the average time a water molecule will spend in that reservoir (table below). It is a measure of the average age of the water in that reservoir, though some water will spend much less time than average, and some much more

oceans (3,200 years)
glaciers (20-100 yrs)
seasonal snow cover (2-6 months)
soil moisture (1-2 months)
groundwater: shallow (100-200 years)
groundwater: deep (10,000 years)

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Ice – The Cryosphere

Back 61

Second only to the oceans as a place to store water
Land ice
Alpine glaciers, ice sheets, ice caps,
10% of the land surface
Oceanic Ice – (size)
Ice pack, ice shelf, ice flow, iceberg

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Land Ice – Glacial Ice

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greenland, high latitudes of north america, antarctica

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Earth’s Largest Ice Pack

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arctic ocean

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oceanic ice forms

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ice pack: an extensive and cohesive mass of floating ice
ice shelf: massive portion of a continental ice sheet that projects out over the sea
ice flow: large, flattish mass of ice that breaks off from larger ice bodies and floats independently
iceberg: a chunk of floating ice that breaks off from an ice shelf or glacier

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Extent of Permafrost

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Permanently Cold subsoil(ground which remains below 0o C for more than two years)

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Surface Water

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Limited amounts
0.25 percent of the world’s total moisture supply

Highly variable in space

Used for drinking water, agriculture
Sustaining human life

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lake

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A body of water Surrounded by land
Natural basin having a restricted outlet
Sufficient inflow of water to keep the basin filled

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reservoirs

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artificial lakes

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Swamps

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A body of water with water-tolerant
plants, predominantly trees

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Marshes

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A body of water with water-tolerant plants, primarily grasses and sedges

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Rivers and Streams

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A natural watercourse flowing towards an ocean or other body of water

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largest drainage basins

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in the middle of continents

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Infiltration Capacity:

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The maximum rate at which water (falling rain or melting snow) can be taken in (absorbed) by soil through the surface.

affected by nature of soil, vegetation, and seasonal factors

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1. The nature of the soil:

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Permeability: the relative ease of movement of ground water through soil. It is controlled by the degree of connectivity between soil pores.

A highly permeable soil is one in which water runs through it quite readily.

Coarse textured soils tend to have large, well-connected pore spaces and hence high permeability. 

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Vegetation

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Plant roots loosen the soil and as a result increase permeability

Plants and plant litter is acting as obstacles (increasing surface roughness) to water flowing over the surface and that gives water a chance to infiltrate.

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Hydroscopic Water

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: Water that is bound to surface of soil particles by molecular forces. This water can not be evaporated, used by plants or otherwise be removed by natural processes.

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Capillary Water

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The part of soil water which is held as a continuous layer around particles. Most of it being available to plant roots.

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Gravity Water:

Back 78

Subsurface water that responds to gravitational force, percolating through the soil.

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Field (Storage) Capacity

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: Maximum capacity of soil to hold water against the pull of gravity.

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Movement of Water Below the Surface

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Capillarity or capillary motion is the ability of a substance to draw another substance into it. It occurs when the adhesive intermolecular forces between the liquid and a substance are stronger than the cohesive intermolecular forces inside the liquid.

Capillarity Moves water firm thick films to thin films

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Gravity Water:

Back 81

Subsurface water that responds to gravitational force, percolating through the soil.

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Ground water

Back 82

Water stored underground
2.5 times that found in lakes and streams
Found in many places, just need to dig
No evaporation
Can last a long time

Water occupying the saturation zone and moving under the force of gravity.

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Saturated Zone:

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: Subsurface zone where all pores of the “ground” are filled with water.

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Water Table:

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The boundary between the unsaturated zone containing Soil Water and the Saturation Zone, which holds the Ground Water.

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Aquifers

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Porous rocks saturated with groundwater

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aquicludes

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layers of impermeable rocks

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confined aquifer

Back 87

creates an artesian well

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Groundwater mining

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- removal of water from an aquifer at a rate
greater than its flow and recharge capacities

Results in:
Collapsing aquifers: water in aquifers often provide support for the porous rock, its removal could result in the rock collapsing, in which case the capacity of the aquifer is greatly reduced
Saltwater intrusion
Contamination of an aquifer by seawater due to over-pumping the aquifer

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Cone of Depression

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Shape of an inverted coneWhen removal of water from well is faster than its replacement

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The Ogallala Aquifer

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Largest Aquifer in the United states
225,000 square miles
Accumulating water for 30,000 years
Water about the size of a larger Great Lake
Only moderate precipitation today
Affected by heavy groundwater mining over the past 100 years, the last 50 especially

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High Plains Aquifer (Ogallala)

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Water table changes from the early 1900s until 1997

water table has dropped more than 40 feet in places
if mining stopped, it would take 1000 years to recharge
water used to irrigate grain crops (wheat, sorghum and corn, providing 40% of cattle feed) and cotton
the City of San Antonio, TX depends entirely on water from the Ogallala aquifer
Underground water does not obey property rights

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Climatic Zones and Types

Back 92

Temperature and precipitation are the most significant and understandable features when classifying climate

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Climate Classification

Back 93

Classification Schemes
Generalize a vast array of data in a simple form
Way to compare/contrast different areas
Examples
Ancient Greek Scheme
Köppen System
Modified Köppen System

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General Bands of Latitude

Back 94

Low Latitude
Between equator and 30° N & S
Midlatitude
Between 30° & 60° N & S
High Latitude
> than 60° N & S
Equatorial
Within a few °’s of the equator
Tropical
Within the tropics
Subtropical
Slightly poleward of the tropics
25-30° N & S
Polar
Within a few °’s of the Poles

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Ancient Greek Classification

Back 95

5 ZONES:

One Torrid
(in tropics)

Two Temperate
(midlatitudes)

Two Frigid

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Köppen System & Modified Köppen System

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Tropical Humid (equatorial regions) (Zone A)
Dry (Deserts: arid & semiarid) (Zone B)
Mild Midlatitude (mild winter) (Zone C)
Severe Midlatitude (boreal, cold winter) (Zone D)
Polar (always cold) (Zone E)
Highland (mountains, plateaus) {addition} (Zone H)

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Modified Köppen System

Back 97

Encompasses basic design of Köppen with minor modifications

3 letter system
First letter climate group (temperature)
Second letter precipitation
Third letter temperature patterns
Csa Mediterranean
C middle latitude temps
s summer dry
a hot summers (as opposed to warm)


Five major climate groupsGroups A, B, C, D, and E14 individual climate typesSpecial category of highland (H) climate

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Different climates as the basis for different biomes:

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Tropical Rainforest
Tropical Deciduous Forest
Tropical Scrub
Tropical Savanna
Desert
Mediterranean Woodland and Shrub
Midlatitude Grassland
Midlatitude Deciduous Forest
Boreal Forest
Tundra

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Climograph?

Back 99

Monthly Temperature&Precipitation

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Tropical Humid Climates (Zone A)
Three types (rainfall based)

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Cover most of the land area with 15-20° of the equator
Lack cold weather
Very wet

1. Tropical Wet - Af

2. Tropical Monsoon - Am

3. Tropical Savanna - Aw

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Tropical Wet

Back 101

Seasonless
Similar weather all the time
Uniform insolation all the time

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Tropical Monsoonal - Am

Back 102

Similar to Tropical Wet
Except heavy rainfall & slightly lower temperatures in summer (high sun season)

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Tropical Savanna - Aw

Back 103

Most extensive of A types
Lesser annual rainfall
Wildfires in dry season
Lowsun dry season

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Dry Climates (Zone B)

Back 104

30% of land area – More than any other climatic zone


Desert – Extremely Arid
Steppes – Semi Arid

Subtropical
Subtropical Desert (BWh)
Subtropical Steppe (BSh)
Midlatitude
Midlatitude Desert (BWk)
Midlatitude Steppe (BSk)

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Subtropical Desert (BWh)

Back 105

Either in or very near subtropical highs e.g. Sahara, Arabian Desert,  Australian, Atacama Desert

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Atacama desert

Back 106

Rainshadow
14 years without precipitation

Deserts
Precipitation
Scarce
Unreliable
Intense
Temperature
Large ranges

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Subtropical Steppe:

Back 107

Around subtropical deserts
Similar temperature
& precipitation (not as extreme)

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Midlatitude Desert:

Back 108

Occur deep in interior of continentsCan have cold winters

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Midlatitude Steppe:

Back 109

Transition zone between midlatitude desert and humid climate

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Mild Midlatitude Climates (Zone C)

Back 110

Equatorward margin of middle latitudesLong and usually hot summersShort & relatively mild winters

Three types
Mediterranean
Humid Subtropical
Marine West Coast

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Mediterranean

Back 111

Western side of continents Influenced by Westerlies Winter wet

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Humid Subtropical

Back 112

Eastern side of continents 25–30º of latitude Higher humidity in summer

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Severe Midlatitude Climates (Zone D)

Back 113

Only in Northern Hemisphere(no landmasses at appropriate latitudes in Southern Hemisphere)Four Seasons with long cold winters
Moderate precipitation

Two types:
Humid Continental (Dfa, Dfb, Dwa, Dwb)
Subarctic (Dfc, Dfd, Dwc, Dwd)

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Humid Continental

Back 114

Between 35 and 55 Degrees in North America Extends to 60 degrees in Europe

Front 115

Subarctic

Back 115

Long, dark, bitter cold winters Summers can be warm – huge ATR
Continentality
Meager precipitation  High mid-latitudes (50° & 70°)
Alaska to Eastern Canada & Scandinavia to easternmost Siberia

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Tundra(ET)

Back 116

Low precipitation, cold,
extremely short growing season,
low primary production – treeline

Front 117

Highland Climate (Zone H)

Back 117

Variation with Elevation

Varies over short distances
Both vertically and direction the slope faces
North versus south facing slopes
Windward vs. leeward

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Biosphere

Back 118

consists of all living things, plant and animal (i.e., flora and fauna).
Processes and interactions within the biosphere are exceedingly intricate – energy, water, & nutrients

Front 119

Biogeochemical Cycles

Back 119

The Flow of Energy
The Hydrologic Cycle
The Carbon Cycle
The Oxygen Cycle
The Nitrogen Cycle
Interrelated and complex

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Flow of Energy

Back 120

Sun is the basic source of energy
Photosynthesis
The production of organic matter by chlorophyll-containing plants and animals
Energy fixed or made stable by plants (Chemical Energy)

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Respiration

Back 121

process of "burning" stored chemical energy, basically through oxidation, for maintaining plant metabolism.

During plant respiration, carbohydrates combine with oxygen and is reduced to carbon dioxide, water, and heat.

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net primary productivity, NPP

Back 122

Plant growth occurs so long as photosynthesis exceeds respiration

Plant growth depends on a surplus of carbohydrate production
NPP is the difference between photosynthesis minus respiration
Measure is Biomass (dry weight of organic material)

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Hydrologic Cycle

Back 123

Most abundant single substance in the biosphere is water

Medium of life processes

Source of their hydrogen
Watery solutions dissolve nutrients and carry them to all parts of the organism

Residence
Bound into plant and animal tissues

Transit
Transpiration-respiration stream

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Carbon Cycle

Back 124

Carbon is one of the basic elements of life
-Carbon based lifeforms

Continuous states of creation, transformation and decomposition

Main components
-Transfere of carbon from CO2 to living matter then back to CO2

-Carbon moves constantly from the living system to organic reservoirs and back.

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Oxygen Cycle

Back 125

O2 is mainly a byproduct of photosynthesis
Other sources...

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Nitrogen Cycle

Back 126

Atmosphere is 78 % Nitrogen
Soil bacteria & cyanobacteria (blue green algae)
Nitrogen fixation
Conversion of the gaseous form to nitrates (usable by plants)
Primarily
Soil microorganisms, plants
Secondary
Lightning & cosmic radiation
Marine organisms
Synthetic manufacture of nitrogenous fertilizers
Nitrogen fixing crops – alfalfa, clover, soybeans

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fundamental units of a food chain

Back 127

plants (autotrophs) fed on by animals (heterotrophs...consumers), which consist of primary consumer herbivores and secondary consumers carnivores

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ecosystems and biomes

Back 128

Ecosystem:
Totality of interactions among organisms and the environment in any area

Applied at many scales

Biome:
large, recognizable assemblage of plants & animals in functional interaction with its environment

Ecotone—the transition zone between biotic communities in which the typical species of one community intermingle with those of another.

Useful for world distribution patterns
Described by their dominant veg. type

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Spatial Groupings of Plants

Back 129

Vegetation Associations
-Emphasis is usually based on the structure and appearance of the dominant plants
1.Forests
-Trees growing close together
2.Woodlands
-Tree dominated – spaced apart
3. Shrublands
-Short woody plants
4.Grasslands
5.Deserts
6.Tundra
7.Wetlands

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The Earth Interior

Back 130

Crust: Outermost solid layer
Makes 1% of the Earth’s volume

Mantle: Beneath the crust & surrounding the outer core
1800 miles – 84% volume

Outer Core: Liquid shell beneath the mantle that encloses Earth’s inner core

Inner Core: Evidently solid, dense, innermost portion

Front 131

Earth’s Crust and Mantle

Back 131

Lithosphere: The uppermost zone of mantle

Asthenosphere: Layer of
upper mantle underlying
Lithosphere
Very hot, weak and easily deformed

Mesosphere: Rigid part of
the deep mantle

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Bedrock

Back 132

(Buried layer of the residual rock that has not experienced weathering and/or erosion)

Front 133

Igneous Rocks

Back 133

(Formed by solidification of molten magma)

Extrusive: Molten rock ejected onto Earth’s surface and solidifies in open air
Intrusive: Rocks that cool down and solidify beneath Earth’s surface

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Sediment

Back 134

naturally-occurring material that is broken down by natural processes, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself.

Front 135

sedimentary rocks

Back 135

Formed by sediment consolidation
by pressure and cementation

Front 136

Formation of Sedimentary Rocks

Back 136

Particles deposited by wind or water
-Layers

Over time builds up
-Compaction

Cementation
-Infilling of pore spaces
--Cementing agent
---Silica
---Calcium carbonate
---Iron oxide

Front 137

Relative Abundance of Sedimentary Rock Types

Back 137

Sandstone
-Compacted sand grains

Shale
-Compacted silt and clay particles

Limestone
-Chemically or organically produced
--Calcium carbonate
--Skeletal remains lime secreting creatures

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Metamorphic Rocks

Back 138

Originally was something else (igneous/sedimentary) but has changed by heat and/or pressure within the Earth.

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Rift Valley Formation

Back 139

Begins on a continent
East African Rift Valley
Grows to become linear sea (“proto-ocean”)
Red Sea
Constructive boundary (rock is created)

Front 140

Plate Boundaries

Back 140

Divergence (Seafloor Spreading)

Convergence (Collision)

Lateral (Transform)

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ocean floor rocks

Back 141

-basalt covered with thin layer of sediments
-oceanic crust

rocks in crust vis a vis surface rocks

Front 142

isostasy

Back 142

vertical movement of the crust to buoyancy in the mantle

-the crust rises and sinks because it is lighter than the underlying mantle

-variations in elevation are due both to thickness and density. the continents stand high because continental crust is thick and light. the ocean basins are low because oceanic crust is thin and dense

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Convergent Plate Boundary: Ocean-to-Continent

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Subduction trenches (“slab pull”) next to continents
Destructive boundary: Rock is destroyed via subduction
E.g., Andes Mountains and Cascade Range

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Convergent Plate Boundary: Ocean-to-Ocean

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Subduction trenches in deep ocean
Destructive boundary: Rock is destroyed via subduction
Island arcs – e.g., Aleutian Islands and Mariana Islands

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Convergent Plate Boundary: Continent-to-Continent

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No subduction
Conservative boundary: Rock is neither created nor destroyed
Folded Mountains: e.g., Himalayas

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Diastrophism

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General term referring to the deformation of the earth’s crust
-Implies the material is solid
-Plate boundary movement

2 Types
-Folding
-Faulting

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Folding

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Occurs when rock is compressed.
-upturned folds are called anticlines
-down turned folds are called synclines
-anticlines and synclines are geologic structures, that is, they are folds in rock material

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faulting

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When enormous stresses build and push large intact rock masses beyond their yield limit, faulting of the surface is likely to occur.  A fault is a fracture along which movement occurs.

The plane that extends into the earth and along which slippage occurs is called the fault plane.

Breaking apart of crustal material
-Displacement

-Occurs in zones of weakness in the crust
-Fault line or zone

-Four types
1Normal
2Reverse faults
3Thrust faults
4Strike-slip faults

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Normal Faults

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Tension stresses
-Pulling apart

Pushed up

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Reverse faults

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Due to compression
Upthrown block rises steeply above the downthrown block

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Strike Slip fault

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movement is horizontal

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thrust

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compression forces the upthrown block over the downthrown block

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Earthquakes

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Vibration of the earth produced by shock waves resulting from the sudden displacement usually along a fault

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p wave

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fastest moving, alternatively compressing and relaxing the material they pass through

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s waves

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slow moving, producing both side to side and up and down motion

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magnitude

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Widely mentioned – least understood
-Calculated on a logarithmic scale
-Difference between small (3) and large (7) is enormous
--1,000,000 times more energy

Common scale
-Richter

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landforms

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Configuration of the land surface taking distinctive forms and produced by natural processes.

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Structural (Initial, Constructional) Landforms

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: Landforms that are created by the solidification of large quantities of magma and/or by massive movements of rock due to plate tectonics.

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Compression

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occurs when rock masses are pushed together like that which occurs when plates collide. Rocks tend to shorten laterally and thicken vertically when exposed to compressional stress

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graben

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downdropped block, often forming a long narrow valley

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horst

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an upthrown block, forming a plateau or mountain

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Earthquakes

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An earthquake is a sudden vibration or trembling in the Earth

Most earthquakes are produced along faults, tectonic plate boundary zones, or along the mid-oceanic ridges

Large masses of rock that are moving past each other can become locked due to friction. Friction is overcome when the accumulating stress has enough force to cause a sudden faults of the rock masses.

The magnitude of the shock wave released into the surrounding rocks is controlled by
the quantity of stress built up because of friction,
the distance the rock moved when the fault occurred,
and ability of the rock to transmit the energy.

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Volcanoes

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A volcano is a conical shaped landform built by the emission of lava and gases from a constricted vent in the Earth’s surface.

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magma chamber

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a huge, subterranean reservoir of molten rock

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central vent

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main conduit through which magma moves toward surface

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lateral vents

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found on the sides of some volcanoes where magma is extruded

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crater

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sits at the top of a volcano and is the location where much of the lava, gas, rock fragments and ash are ejected from

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lava

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word for magma (molten rock) when it erupts onto earth's surface

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tephra

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general term for fragments of volcanic rock and lava regardless of size that are ejected from the volcano.

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classification of volcanoes based on:

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the magma chemistry,

explosiveness of the eruption,

the geomorphic form.

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Basalt plateau (Flood Basalts)

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Basalt plateaus occur mainly in tectonic divergence zones and “hot spots”.

Extensive continental deposits of basaltic volcanic rock

Very fluid basaltic magma with horizontal flows.

Form is flat

Can occupy an area from 100,000 to 1, 000,000 km2.

Lava deposit can be up to 1,800 m thick.

The least explosive type of volcano

Some basaltic magmas can produce very large slightly sloping volcanoes, 6 to 12°, that have gently flowing magmas called shield volcanoes

Shield volcanoes can be up to 9000 m tall

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Hot Spot

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A volcanic area on the surface of the Earth created by a rising plume of magma.

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Cinder Cone

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small volcano, between 100 and 400 meters tall, made up of exploded rock (tephra) blasted out of a central vent at a high velocity.

They form when large amounts of gas accumulate within rising basalt magma.

The rain of tephra accumulates around the vent to form a roughly circular hill

Rarely grow more then few hundred meters

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Composite volcanoes

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are made from alternate layers of viscous lava flows and tephra

Form from alternating eruptions dominated by tephra or lava. As a result, composite volcanoes display layers of these alternating flows.

The chemistry of the magma is quite variable ranging from basalt to granite.

Magmas hold large amounts of gas under high pressure, and can produce highly explosive eruptions of tephra along with white-hot gases and fine ash.

Conical in Shape. Height ranges from 100 to 3500 meters tall.

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Calderas

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When a stratovolcano has a very violent eruption it is possible for the entire central portion of the volcano to be destroyed. The volcanic mountain may actually collapse in on itself forming a large depression, called a caldera.

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volcanic neck

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As volcanic activity subsides, magma may cool in the central vent and, over thousands of years, the overlying cone is worn away to expose the harden rock inside

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dike

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Radiating away from the central vent may be  nearly vertical fractures into which magma can intrude and cool. Erosion of the overlying surface reveals a linear, fin-like ridge radiating away from the volcano

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mountain

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can be defined as an area of land that rises abruptly from the surrounding region.

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mountain range

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a succession of many closely spaced mountains covering a particular region of the Earth.

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mountain belts

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belts consist of several mountain ranges that run roughly parallel to each other. (The North American Cordillera, the Himalayas, the Alps, and the Appalachians are all examples of mountain belts that are composed of numerous mountain ranges.)

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Some mountains are volcanic in origin forming where rising magma breaks through the Earth's surface. Volcanic mountains tend to have sporadic distributions within a mountain range or can occur alone because of a localized hot spot.

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Denudation

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: total action of all processess whereby the exposed continental rock are worn down and removed.