Geology Exam 3

Front 1

Erosion is an external process that shapes the crust. For example

Back 1

In the same way plate techtonics are driven by the earth's heat engine, erosion reduces higher elevation because of energy from the sun and force from the earth's gravity.

Front 2

What is the proper definition for EROSION?

Back 2

Erosion is defined as, "Downhill motion of materials under the influence of gravity."

Front 3

Erosion usually involves some fluid or medium to move the materials. What is the most active of these media that is used to move the materials?

Back 3

The most active media that moves materials in erosion is water-both liquid and ice formation.

Front 4

What are the two ways erosional processes are classified?

Back 4

1. Erosion without a medium
and
2. Erosion with a medium

Front 5

First let's examine erosion without a medium (mass wasting is what is used in erosion that is classified as erosion without a medium)

Back 5

There are two kinds of mass wasting: slow mass wasting and rapid mass wasting.

Front 6

Slow mass wasting is the slow downhill motion of materials under the influence of gravity.

Back 6

Regolith, "lith" meaning stone and "rego" meaning blanket or resin. This combo of soil, sediment, ect. called regolith is moved downhill by gravity. This erosional process is called slow mass wasting.

Front 7

Slow mass wasting therefore is the dominant process that moves regolith slowly downhill.

Back 7

Slow mass wasting brings regolith down to streams. The streams then pile up on coastal lines and the edge of continents then are the place the slow mass wasting brought the regolith.

Front 8

The regolith expands and contracts because of clay materias which expands when wet and contracts when dry and also because of soil which gets wet and freezes and therefore expands and then when the ice thaws the soil shrinks again.

Back 8

Creep is the slowest form of mass movement, measured in millimeters or centimeters per YEAR and occurring on virtually all slopes.

Front 9

Moisture is critical because in low-moisture areas there is limited creep and so materials along sides of a valley don't get pulled down at the same rate, so the valley walls remain upward, forming canyons.

Back 9

Geographically, slow mass wasting is central in moving sediments downhill and, along with the help of streams mass wasting shapes the landscapes in many places.

Front 10

Rapid mass wasting on the other hand, though not as geologically important as slow mass wasting, can be devastating.

Back 10

Two dangerous examples of rapid mass wasting are the 1970 Peru landslide that ended 22,000 lives. Another is the 1963 Italian dam rupture caused by a rock slide, that killed over 2,500 people.

Front 11

Rapid mass wasting is caused by other factors. Like the earthquake that caused the Peru landslide or the rock slide that caused the ruptured dam in Italy.

Back 11

The eight causes of Rapid mass wasting are 1. oversteepening 2. overloading 3. makeup of materials 4. topography (steepness) 5. vegetation 6. water 7. structure (layout) 8. triggers (sudden vibrations ect)

Front 12

The eight causes of mass wasting defined are

Back 12

1. Oversteepening causes rapid mass wasting because different materials fall at different steepness' and there is no one-size-fits-all for steepness safety. For example, a penny would slide down a sinking ship a lot quicker than a vehicle would.

Front 13

2. Overloading causes rapid mass wasting because additional weight being placed on a critical angle may not be able to support the extra weight. Like a 50 pound child being supporting by a diving board but a 400 pound man would not be supported.

Back 13

3. Type of materials affect rapid mass wasting because weaker slopes that are made out of loose materials will move more readily than coherent resistant rock. For example, I can blow dust out of my hand but not boulders off a cliff.

Front 14

4. Topography affects rapid mass wasting because the steeper the slope the greater the chance of movement. For example, anything has a greater chance of being pulled downward if the hill is almost vertical as opposed to a slight elevation.

Back 14

5. Vegetation- trees and plants prevent the saturation of soils by transpiring moisture which lubricates movement which prevents slopes being stabalized with plant roots.

Front 15

6. Water causes rapid mass wasting because the increase in water pressure will make the soil more porous and add weight to the slope, making it less stable.

Back 15

7. The structure of the materials can cause rapid mass wasting because the way the sediment is layered, folded and has faults. It is like the crane game- the way the animals are stuck in the machine determines the stability.

Front 16

8.Triggers can cause rapid mass wasting through earthquakes, sudden sounds, and vibrations.

Back 16

The hydrolic cycle: It is not WHERE water is stored or HOW MUCH water is stored there, but it is MOTION that is critical to shaping landscapes.

Front 17

The amount of water on our planets surface makes it unique to all the known planets in our solar system.

Back 17

Oceans make up about 97% of all the water on earth. The rest is in glaciers, lakes, rivers, groundwater and the atmosphere.

Front 18

Water is in a constant cycle, being driven by the sun. Water evaporates from oceans, most of it condenses into clouds and then precipitates immediately, which puts it right back into the ocean.

Back 18

So some of the ocean water in the hydrolic cycle is evaporated at the ocean, and then precipitates right back into the ocean.

Front 19

The moisture that is left over and not back in the ocean is evaporated and transported by the winds to land.

Back 19

So some of the water gets put right back in the ocean and some of the water is trasported to fall on land in the shape of rain, snow, hail or sleet.

Front 20

From the land, water's trek back to the ocean takes on many routes.

Back 20

Snow for example, forms glaciers and the glaciers move downhill and melt. Then the melted glacier will mix with surface or ocean water.

Front 21

Another way rain that falls on land can be routed back to the ocean is by means of travel with streams (rivers). The streams collect the rain and return much of it to the oceans at some point.

Back 21

Another way rain that came from the ocean can be transported back to the ocean is by sinking below the surface and seeping downhill as ground water.

Front 22

However, most of this water, this melted-glacier or snow or land-seeped groundwater, that is all trying to transport back to the ocean...will never make it back. Most of it will be evaporated on land.

Back 22

By recycling rainwater though, evapotranspiration nearly triples the available water supply on land!

Front 23

Glaciers move so slow that they don't really affect the shape of landscapes all that much.

Back 23

The most effective erosional agents on the surface of the earth are STREAMS.

Front 24

Streams are bodies of water moving downhill in a channel.

Back 24

Streams are the most effective erosional agents on the surface of the earth.

Front 25

Streams are responsible for shaping most of the landscape features that develop, even in deserts.

Back 25

How Streams Form: Water hits the surface and either gets sucked up or becomes runoff.

Front 26

What factors determine how much water gets sucked up versus turned into runoff?

Back 26

The amount of runoff is controlled by a series of factors like the type of materials that are sucking up the water, the degree of saturation (if the surface is really thirsty or full of water), how steep the slope might be, how hot the sun is (causing higher amounts of evaporation) and even vegetation amounts and types. All these things can effect how much water is going to be runoff.

Front 27

STREAM INPUT- The order of stream formation is as follows: rain--->sheet flow (which is barren areas can cause sheet erosion)
--->water collections in rills or gullies--->channels enlarge as a result--->channels that collected the water carry it downSTREAM.

Back 27

So its like this: rain, sheet, rills/gullies, channels, streams.

Front 28

STREAM OUTPUT-Stream Drainage: watershed in the upper portion that picks up eroded sediments (think tree limbs)
--->The thicker middle portion of the stream transports water and sediments (think of tree trunk) ---> at the lower reaches of the stream, the mouth of the stream, the stream deposits the sediments. (Think seeds falling to the ground from a tree and being deposited into the soil).

Back 28

Kinetic energy causes streams to move. The amount of kinetic energy is determined by the mass (weight) and velocity (speed).

Front 29

The energy required to move a stream and do stream processes depends on how much weight and speed the water and sediments have.

Back 29

What determines the speed (velocity) of th water? Some examples of things that control velocity (speed) are gradiant (meaning slope), friction, channel shape and roughness, channel size, the amount of water (the discharge), and sediment load.

Front 30

These elements impact velocity which impacts kinetic energy which impacts the streams ability to move.

Back 30

Streams erode in 3 ways: solution, abrasion, and hydrolics.

Front 31

The way streams erode in solution is that limestone and other soluable terranes have newly dissolved materials added to the ions (elements) that were introduced to the stream by weathering.

Back 31

So streams erode by solution mixture reacting from certain minerals within the stream and elements that came from out of the stream by weathering process.

Front 32

The way streams can erode in abrasion is that different pieces of older rocks called clasts can scour the stream through physical impact.

Back 32

So streams can erode by solution and by abrasion, and the abrasion happens when clasts hit stuff and causes erosion.

Front 33

The abrasion casused by the solid clasts has been known to cause potholes. Meaning little pebbles swirlingover long periods of time can literally cut potholes into the bottom of the river.

Back 33

Sediments are being eroded and transported by streams. Continents lose their soils and regolith to streams at the rate of nearly 3 inches every 1000 years, meaing the Rocky Mountains will be gone in only 50 million years.

Front 34

Transport and Deposit processes: Streams carry sediments in two ways- either in clastic loads (clastic particles) or chemical loads (dissolved ions).

Back 34

The clastic load has heavy clasts roll on the bottom of the stream, lighter bouncing saltation load (sand) that literally bounces along the bottom and finally the lightest are silts and clay called the flotation load- floating with the stream flow.

Front 35

So
bottom=clastic load rolling
middle=saltation load bouncing
top=floatation load floating

Back 35

To measure a streams transport power we look at two measurments: capacity and competency.

Front 36

Measuring a stream's transport power by capacity means looking at the total amount of materials it moves.

Back 36

Measuring a stream's transport power by competency means looking at one particle, the largest partical a stream can move at any given time.

Front 37

Overtime, finer sediments are carried off while courser sediments are left behind, meaning the particles in the sediment become sorted according to size. As the particles travel they get rounder and smoother because of abrasion. The sediments are being softened and chemically weathered and are essentially changing in composition. This is called maturity.

Back 37

So maturity is the extent which sediments have been modified.

Front 38

Since transport power depends on energy, the higher the energy the higher the transport power. For example, in floods, energy goes up, transport power goes up, capacity goes up, competency goes up, and cutting power (amount of abrasion) goes up. Pebbles which used to be part of the traction (bed) load are now playing the roll of bouncing saltation load. The sand which used to be part of the bouncing load saltation load is now the top floating load.

Back 38

so when energy increases, cutting power (abrasion) and erosion, competency and capacity all increase. So when energy decreases, the erosional processes decrease.

Front 39

When energy decreases the capacity decreases,and the competency decreases. When the energy is low, the river deposits the largest clasts first.

Back 39

Transport is really a steady state condition between erosion and deposits.

Front 40

After a long time, a stream will adjust itself so that its water, sediment loads, and deposits at the mouth will EQUAL the amount of erosion happening at the headwater.

Back 40

A stream will, in other words, become a dynamic equalibrium when its water, sediment loads and deposits are equal to its erosion at the headwaters.

Front 41

Valley Evolution - streams create and change the valley that they flow in.

Back 41

How to streams change their own course? (by 3 ways-deepening, lengthening and widening thier valleys)

Front 42

Headwaters are the areas of erosion that are dominated by "downcutting."

Back 42

Downcutting is "lengthening the valley." The way downcutting lengthens the course of a stream's valley is by water rushing DOWNhill in a mostly straight, narrow and v-shaped way.

Front 43

Along with downcutting, another way streams can change the shape of its valley is by deepening its channel. As the channel deepens, mass wasting (sediments moving downward under pressure), begins to drag new materials into the stream and the valley widens. New mini-streams (tributaries) contribute their waters and loads of sediments into the origional stream.

Back 43

So, downcutting lengthens the stream, mass wasting deepens the stream, and the deepening of the mass wasting widens the stream.

Front 44

The main channel during a flood is the area of maximum speed (velocity).

Back 44

If sea levels rise, streams deposit more. If sea level falls, streams begin a new cycle of erosion.

Front 45

When sea levels drop and streams deposit sediment, it can form terraces. Either from erosion or deposits, terrace happens when streams abandon one floodplan to form a new floodplan.

Back 45

An amazing example of a terrace evolving from erosional or depositional changes is the Grand Canyon. The Colorado River began downcutting and created the canyon.

Front 46

Human influence on streams. Over the last few centuries, man has been the cause of changes in streams.

Back 46

Because of agriculture being introduced 10,000 years ago- human colonization rapidly moved to more fertile river valleys.

Front 47

Streams react to human interference. For example, a stream's equilibrium is offset by man-made dams. Dams are put in place to supposedly store large water supplies but the opposite is the result.

Back 47

When a dam is created by man for a large water storage, actually fills the reservoir with sediment which defeats the purpose of the dam in the first place.

Front 48

The problem with man putting a dam in a stream is that because the water no longer has the sedament load to deposit downstream, the valley begins to erode. There are no more silts and clays to be deposited so the valley doesnt get replenished. This makes it necessary for man-made chemical fertilizer to replace what the stream had applied. So from dams to chemical fertilizer applications to chemicals seeping into the ground and causing pollution, human influence on stream processes are heavy.

Back 48

Another way humans mess with streas is by trying to channel the rivers and streams to decrease small flood hazards. The problem is that these tiny flood - stoppers, when broken, pools out water into the flood space which prevents it from flowing back into the river. The flood stoppers do stop tiny floods, but when big floods happen they last much longer and are stronger because of it.

Front 49

Runoff is rain and sediment that is not sucked up by the earth and has to therefore flow somewhere.

Back 49

Aggrivated streams are a result also of agricultural practices such as plowing, which tripled the sediment load that rivers must handle.

Front 50

Another way humans mess with streams is by increasing runoff through deforestation and urbanization.

Back 50

Streams and plate techtonics: Streams create divides, streams raise and lower sea levels, streams determine the base level, and even affect the size and height of continents.

Front 51

Ground water- is a water that is sucked into the earth surface.

Back 51

The earth has to be permeable, which means the earth has to allow water to pass through it in order for groundwater to be successful.

Front 52

What does permiability depend on?
Porosity and size/degree of interconnection.

Back 52

Permiability depends on how porous the ground is meaning how much void space is available to be filled with water.

Front 53

Permeability not only depends on porousity, but also on size and degree of interconnection.

Back 53

What is the zone of saturation? The space that was once porous with air and is now saturated with water.

Front 54

What is the zone of aeration? it is the area ABOVE the zone of saturation where the spaces still contain air.

Back 54

The zone of saturation, which is filled with water, has a top layer called the water table.

Front 55

What are aquifers?
Layers of rock that have been saturated.

Back 55

What are aquacludes? Layers which prevent water from percolating.

Front 56

Aquafers=saturated rock
Aquacludes=dry and closed off rock-prevent percolation.

Back 56

In unconfined flow areas, water seeps through openings in all rocks like a sponge, balancing itself out in response to gravity.

Front 57

In a confined flow area water is trapped below an aqualude (a non-permeable rock) which prevents the water from rising to its normal level.

Back 57

So,
Unconfined flow=water balances like a sponge

Front 58

Confined flow=water trapped below non-permeable layer.

Back 58

When the non-permeable aquaclude is breached, this is called an ARTESIAN.