geology test 4

law of superposition

in an undeformed sequence of sedimentary rocks, each bed is older than the one above it.

principle of original horizontality

layers of sediment are generally deposited in a horizontal position.

principle of cross-cutting relationships

in order for the fault to cut those layers they had to be there already

inclusions

pieces of one rock unit that are contained with another

unconformities

breaks that interrupt the deposition of sediment

angular unconformity

tilted rocks overlain by horizontal rocks

disconformity

missing time between two sedimentary layers

nonconformity

when you have an igneous or metamorphic rock overlain by a sedimentary rock

half-life

the required time for half of the nuclei of a sample to decay is called the half life of an isotope

replacement

type of fossilization when hard parts are replaced with a harder material as water flows through

petrified

type of fossilization when the original material is organic and replaced by silica or pyrite then it is called petrification

mold

if the body is buried then decays, a hole may be left where the body was mimicking the shape of the remains

cast

the shape made when a mold is filled in

carbon-rich plant preservation

carbon plants may leave a thin film that is preserved in materials like silt

impressions

pattern left on a fine-grained material

index fossils

allow us to date the layers they are in

precambrian

earliest life on earth, comprises nearly 90% of geologic time but only simple forms of life existed during this time. nothing with hard parts.

paleozoic

this time was dominated by several major groups of marine animals including corals, creatures likes clams and various types of fish. The end of this time is called the Great Dying

mesozoic

This is the age of dinosaurs. the end of this time is marked by the extinction of dinosaurs.

cenozoic

the age of mammals, most recent

hypocenter

the point at depth within the earth where the earthquake occurred

epicenter

the point at the surface above the hypocenter where the earthquake occured

normal dip slip fault

reverse dip slip fault

strike slip fault

fault scarp

a cliff where a fault meets the earth’s surface

surface waves

travel on or near the earth’s surface

body waves

travel through the earth

P waves

the primary set of waves, can move through solid and liquid materials

S waves

the secondary set of waves, move through solids but not liquid

richter scale

takes into account the distance from the epicenter and the amplitude of the wave

modified mercali scale

considers the effects of shaking on people, structures, and surroundings

spring tide

When the sun and moon are on opposite sides of the Earth both exerting pull there will be the largest difference between high and low tide.

neap tide

when the sun and moon are at right angles to each other.

delta

Where a river enters the ocean a __________ forms

sea cliff

Hard rock eroded into cliffs along shore.

sea arches

As cliffs are undercut caves or arches are formed.

wave cut platforms

Waves cut notches cut into cliffs which eventually form a platform.

sea stacks

Continued erosion of arches or caves leaves rocks in the ocean.

spit

a sand bar that extends part of the way across the bay

groins

built perpendicular to the beach into the water to influence the lateral transport of sand.

jetties

These are built in pairs typically on each side of a bay to keep sediment from closing off the bay

sea level rising

Estuaries are a sign of

alpine glaciers

Glaciers that flow out of the mountains into broader open areas

calving

As a glacier meets a lake or ocean, Parts of the glacier may break off into the water

medial moraine

Sediment that is deposited in the center where two glaciers join

arete

Large jagged ridges that occur where two cirques meet are an erosional feature

frost wedging

There is a crack and water fills in the crack. At night it drops below freezing and the water turns to ice and expands making the crack slightly larger.

salt crystal growth

This occurs in rocks along rocky shorelines where salt water moves into the cracks and salt precipitates out. The salt crystals enlarge the cracks in the rocks.

sheeting

When large masses of igneous rock, particularly granite, are exposed by erosion, concentric slabs begin to break loose.

oxidation

oxygen dissolving in water on iron-rich minerals

O horizon

top layer made mostly of organic material

A horizon

under O horizon, mostly mineral matter but lots of biological activity and humus

E horizon

under A horizon, light in color and contains little organic material

over steepened slopes

trigger of mass wasting events when erosion or human activity makes land at more of an angle

earthquakes

shaking can trigger mass wasting events by disturbing loose material

vegetation removal

triggers mass wasting events because there is nothing for the soil to hold onto

noise

vibrations can cause avalanches

blasting

using nearby explosives can weaken slopes

freefall

falling without disruption

slides

when the material slides along zones of weakness down a slope

flow

has the most water, and occurs when material moves downslope as viscous fluid

slump

downward sliding of a mass of rock or unconsolidated material as a unit along a curved surface

rockslides

occur when blocks of bedrock break loose and slide down a slope

lahars

Debris flows composed mostly of volcanic material on the flanks of a volcano

earthflows

When water saturates the soil and regolith on a hillside, the material may break away, leaving a scar on the slope and forming a tongue- teardrop- shaped mass that flows downslope

creep

Involves gradual downslope movement of soil and regolith

laminar flow

stream flow parallel to the shoreline

turbulent flow

more the norm, swirling, erratic flow

dissolved load

will depend on the rock type and whether it is easily dissolved in water

suspended load

material that can be carried along in a stream. Typically only fine grained materials are carried

bed load

movement along the bottom of the stream

capacity

is the maximum load of solid particles that a stream can transport

competence

the largest particle a stream can carry

settling capacity

the amount of energy required to allow sediment to settle out of the water

sorting

occurs as velocity slows down slowly the first thing to drop out will be the larger particles as it continues to slow down the smallest particles will drop out

alluvium

a general term for all stream deposited sediment

bars

channel deposits usually composed of sand and gravel

braided stream

stream with many bars

narrow valleys

associated with high slopes, rapids, and waterfalls

wide valleys

associated with lots of curves, floodplains, and sediment

point bar

the depositional feature found on the inside of a meander where the energy is lower and sediment is deposited in a crescent shape

cut bank

erosional feature found on the outside of a meander where the energy of the stream flows into the bank causing erosion

oxbow lake

a curve in a stream becomes so severe that the stream cuts through the banks and finds an easier way to flow

dendritic

common drainage pattern, looks like branching

radial

associated with volcanoes or domal uplifts

rectangular patterns

follows the joints between bedrock

stream piracy

occurs when a stream erodes headward and then capturing a stream from a different basin

water table

point below which all pore spaces are filled with water

zone of saturation

areas where all pore spaces are filled with water

zone of aeration

zone where pore spaces contain air and water

capillary fringe

area where water tension pulls water up slightly at the edge between the water table and the aeration zone

porosity

the amount of void spaces in a rock or sediment

permeability

the ability of a material to transmit fluid

specific yield

the portion of water which will drain or move through a material under the influence of gravity

specific retention

how much water is retained by the sediment

aquifer

is a rock layer or sediment which has a high porosity and high permeability

aquitard

have little permeability

hot springs

This water has typically flowed near a magma to get heated

geysers

pressurized fountains of water