Essc 110 Exam 2

Front 1

Metamorphism

Back 1

transformation of one parent rock into another. Created from pre-existing igneous,sedimentary, and metamorphic rocks

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Contact(thermal) metamorphism

Back 2

exposed to high temperature from magma

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Regional metamorphism

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Parent rocks exposed to direct pressures and high pressures during mountain building

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Solid state

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intense temperature and pressure where grains, atoms or molecules of a rock or mineral are packed closer together, creating a new crystal structure.

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Agents of metamorphism

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Heat

Pressure:

Confining pressure - Even in all directions, increases with depth

Differential stress - uneven direction, occurs during mountain building and causes deformation

Chemically active fluids - Promotes re-crystallization perpendicular to the stress

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Re-crystallization

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Occurs under intense temperature or pressure and is when atoms or molecules of a rock or mineral are packed close together causing a new crystal structure to be formed

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Metamorphic textures

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Low grade metamorphism - denser compact rocks - Slate

High grade metamorphism - results in mineral re-crystalization - Schist, Gneiss

Foliated texture - minerals are in a parallel alignment

Nonfoliated texture - rocks contain crystals

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Metamorphic facies

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Groups of minerals distinctive of certain metamorphic rocks. These minerals form in a pressure-temperature field. This links them to specific tectonic settings

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Groundwater

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94% of liquid freshwater on the planet. Water present in pore spaces in soils and sediments. Also in joints and fractures in bedrock.

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Groundwater geological roles

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Erosional agent that produces sinkholes and caverns

Equalizer of streamflow - large percentage of precipitation soaks into the ground moving into stream channels

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Effects on level of groundwater

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Steepness of slope

Nature of surface material

intensity of rainfall

type and amount of vegetation

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Zone of soil moisture

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water is held by molecular attraction as a surface film on soil particles

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Unsaturated zone

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pore spaces in the material that are filled mainly with air

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Zone of saturation

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all pore spaces are filled with water. groundwater resides here

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Water table

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upper limit of the zone of saturation. Water table is usually a replica of the surface. It is affected by the velocity of groundwater and variations of rainfall and permeability

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Porosity

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determines amount of storage of groundwater

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Permeability

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ability to transmit water

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Aquitard

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impermeable layer of material that prevents water movement

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Aquifer

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Permeable layer of material that transmits groundwater freely

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Confined aquifer

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an aquifer contained underneath an aquitard

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unconfined aquifer

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an aquifer below the surface that is not obstructed by an aquitard

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Groundwater movement

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Very slow movement

driven by gravity and water pressure

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Darcy's law

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Q(Volume)= A(area)*K (permeability)*HG(Gradient)

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Wells

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Holes drilled into the zone of saturation

Pumping can cause a drawdown or lowering of the water table

drawdown causes a cone of depression in the water table

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Artesian

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Groundwater rising above the sea level in which it was originally found

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Artesian wells

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water rises sometimes overflowing at the surface

Two conditions are necessary: Water confined to an inclined aquifer where one end is exposed to the surface and confined aquifers

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Springs

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Natural flow of groundwater that occurs whenever the water table intersects ground surface

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Hot springs

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hot water heated by groundwater circulating at great depth

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Geysers

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regularly discharging Columns of water that are hot springs

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Land subsidence

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areas with thick layers of loose sediments where withdrawal of groundwater is less than discharge

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Saline intrusion

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Salt water entering groundwater

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Caverns

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erosion specific caves that are created at or below the water table in zones of saturation

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Dripstones

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Calcite deposited as water drips

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Stalactites

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Hold tight to the ceiling

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Stalagmites

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grow from the floor might trip over

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The hydrologic cycle

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Begins with the evaporation of water from the surface of the ocean. As moist air is lifted, it cools and water vapor condenses to form clouds. Moisture is transported around the globe until it returns to the surface as precipitation.

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Runoff

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Water that is traveling down a slope and starts off as a sheet flow but then develops into channels which are called rills

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Downcutting(Vertical erosion)

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Process that deepens a stream channel

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Headward erosion

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process that lengthens a stream channel up its slope

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Drainage basin

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land area that contributes water to a river system. A divide separates drainage basins

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Streamflow

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Ability of a stream to erode and transport materials depending on its velocity

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Flow discharge equation

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Area*Velocity

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Streamflow velocity factors

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Gradient(Slope)

Channel characteristics

Discharge

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Erosion factors in rivers

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Scouring - Removal of loose fragments/sediments

Breaking and lifting

Abrasion: water carrying sand can grind away at channel floor and walls

Dissolution(Breakdown)

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Transportation of sediments

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Dissolved load (In solution)

Suspended load (in suspension)

Bed load (moved along bottom)

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Sediment load

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transported material in the river

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Settling velocity

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refers to the different levels of velocity that can grab different materials

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Competence

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maximum particle size that can be transportedin a stream

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Capacity

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Maximum load that can be carried. is related to the discharge

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Deposition

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When materials are dropped by a decrease in the velocity of the water flow. Materials drop out in order of size (sorting)

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Alluvium

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deposits of stream sediments

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Bars

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Temporary deposits of sediments

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Deltas

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Exist where a stream reaches the ocean and the velocity is rapidly decreased creating a large buildup of sediments

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Natural levees

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form parallel to the stream channel

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Alluvial fan

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A deposit of sediment that is created when water velocity is decreased suddenly

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Stream profile

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Side view of a river. Gradient decreases along the profile. Discharge tends to increase downstream in humid regions

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Base level

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Lower limit to how deep a stream can erode

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Ultimate base level

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sea level

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River system

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rivers and streams contributing to the formation of landscape and consists of three parts:

Zone of erosion

Zone of transport

Zone of deposition

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Stream valleys

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Valleys shaped by Weathering, overland flow, and mass wasting

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Narrow valleys

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Downcutting towards base level and often include rapids and waterfalls

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Wide stream valleys

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creates flood plain

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Meandering stream

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streams that move in sweeping patterns and transport most of their load in suspension. deep and smooth channel

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Cut bank/Point bars

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Cutbank - the outside of a curve where sediment is built up

Point bars - the inside of a curve where sediment is built up

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Oxbow lakes

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when a meander is cut off by sediment and is a standalone lake

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Natural levees

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Build on sides of a stream and caused by repeated flooding.

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Glacier

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thick mass of ice that forms over land due to accumulation, compaction, and re crystallization of snow.

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Types of glaciers

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Alpine glaciers - formed in high mountain areas

Continental glaciers(ice sheets) - large scale at high altitudes

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Alpine or valley glaciers

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usually follow valleys formed by streams

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Continental glaciers

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Only two on earth and cover 10% of land area

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Glacial flow

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Glacial movement.

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Plastic flow

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movement in the ice below 50 meters

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Slipping

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Movement of the entire mass underground

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Zone of fracture

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upper 50 meters of brittle ice that cracks forming crevices

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Zone of accumulation

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area where a glacier forms

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Zone of wasting

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area where there is a net loss due to melting

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Calving

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Melting and large pieces of ice falling off the front of the glacier. If the glacier is meeting a sea these create icebergs

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Glacial movement

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if accumulation is higher than ablation, the glacial front advances.

If they are the same, the glacier remains stationary

if ablation is higher than accumulation the glacier will retreat

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Plucking

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rock blocks are lifted and incorporated into the rock

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Great lakes formation

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Formed at the end of the last ice age. Basins carved by glaciers

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Present ice age

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Occured during the Pleistocene epoch

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Milankovitch hypothesis

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Explains how glaciers were formed based on variations in earth's orbit that causes changes in solar insolation

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Eccentricity

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Shape of earths orbit

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Obliquity

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angle of earth's axis

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Precession

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axis wobbles

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Earthquake

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the sudden release of stored energy in the form of waves called seismic waves. associated with movement along faults

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Seismology

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Study of elastic waves that travel through the earth.

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Seismograph

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instrument that records earthquakes generating seismograms

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Wave frequency

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measurement of how fast a wave travels

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Wave amplitude

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measure of how strong a wave is/intensity

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Focus

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Place where earthquake waves originate from in the earth

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Epicenter

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Area on the surface above the focus

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Elastic rebound theory - explains earthquakes

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energy accumulates on opposite sides of a rock. This causes the rock to deform. When the internal strength of the rock is overcome there is a sudden movement that occurs along the fault. energy is then released and rocks snap back into their original shape.

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Hanging wall

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the block of rock above the fault line

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Footwall

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The block of rock below the fault line

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Normal fault

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hanging wall moves down. Prevalent at spreading centers

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Reverse and thrust faults

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Hanging wall block moves up

Reverse fault - dips greater than 45 degrees

thrust fault - dips less than 45 degrees

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Strike slip faults

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dominant displacement is horizontal and parallel to the fault

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Foreshocks

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shocks before an earthquake

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Aftershocks

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shocks after an earthquake

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Seismic waves

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Waves that are above the ground. slowest velocity

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rayleigh waves

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travel as ripples

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love waves

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Shear waves

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body waves

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travel through the earth

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Primary waves

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Compressional waves, greatest velocity

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Secondary waves

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Shear waves

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Intensity

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the effect of the earthquake on the surface. Measured by the modified mercalli intensity scale

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Magnitude

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measure of earthquakes in terms of the energy released. Measured on the richter scale

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Movement magnitude scale

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derived from the amount of displacement that occurs along the fault zone

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mountain coverage

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mountains cover 24% of the earth's surface

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Mountain range

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a group of adjacent mountains that are geologically related

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Mountain system

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a group of adjacent mountain ranges geographically related

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Mountain belts (orogens)

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composed of mountain systems

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Compression forces

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squeeze and shorten

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tensional forces

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stretch and pull apart

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shearing forces

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push two sides in opposite directions

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Ductile material

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undergoes smooth , continuous plastic deformation and do not spring back to their original shape when the deforming force was released

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Syncline

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A trough or fold. regular v

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Anticline

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A ridge shaped fold. upside down v

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monocline

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a bend in a continuous shape

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plunging fold

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A fold with an inclined axis. So a fold up or down

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structural dome

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intersecting anticlines

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Structural basin

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inverse of domes and are a depression