geology exam 2

earthquakes

vibration caused by sudden breaking/ frictional sliding of rock in the earth

what causes earthquakes

geological processes":

• magma intrusions

• tectonics

• landslides

• humans (nuclear testing, seismic wave generation)

• faults

faults

fractures where one body of rock slides past another

• normal fault

• reverse fault

• strike slip fault

footwall

the fault surface you can stand on/ see

hanging wall

the fault surface you cant see

normal fault

hanging wall moves down from footwall

• at divergent boundaries —> pulled apart

reverse fault

faults push together to make hanging wall go up

• at convergent boundaries —> pushed together

strike slip fault

faults slide past each other; no vertical placement

• transform boundaries

how faults cause earthquakes

force/ stress is applied to earth’s crust —> crust bends and snaps —> releases seismic waves

• bc continental crust is brittle

focus

where fault slip begins underground

epicenter

point of earthquake on earth’s surface above ground

what seismic stations tell you about earthquakes

• 1 seismic station —> location of earthquake, NOT DIRECTION

• 3 seismic stations —> knows EXACT location of epicenter

mercalli scale

measuring earthquake based off intensity (how much ground is shaking)

• perception of the ppl (kinda subjective)

• 1-10 intensity scale (1 = not felt, 10 = crazily intense)

richter scale

measuring earthquake based off the magnitude (amt of energy released/ amplitude)

• calculated by distance of earthquake and amplitude

which layer of earth earthquakes happen

only in lithosphere (upper mantle and crust)

mexico city earthquake

mexico city = not close to epicenter but still got shakes —> land used to be lake texcoco (vulnerable/ muddy land) —> vulnerable to seismic waves

earthquakes: Tohoku 2011 and Indian Ocean 2004

9.1 earthquakes (super intense) —> HUGE tsunamis

how earthquakes cause tsunamis

convergent boundaries subducting

• overriding plate gets stuck but subducting plate keeps moving —> crust bends up —> intense waves

how volcanoes effect climate

large eruptions —> reduces sunlight —> decreases average temperature/ weather (bc extreme soot/ CO2)

• ex: year w/o summer 1816 in Europe (Mt Tambora erupted —> messed up sky w/ eruption)

sediments

loose, solid pieces of rocks/ minerals that get transported by wind, water, ice and are eventually deposited by the slow down of the transporting fluid

sedimentary process

1. make sediment

2. move sediment

3. deposit sediment

4. lithify sediment

erosion

rock, soil, dissolved material that is removed from one location and moved to another location

weathering

physical disintegration and chemical decomposition of older rock to produce solid particulate residues and dissolved chemical substances

mechanical weathering

physical disintegration

1. thermal expansion

2. freeze thaw weathering

3. abrasion

4. stress release weathering

5. exfoliation

6. salt weathering

thermal expansion weathering

heat applied to rock —> rock doesnt have enough space to accommodate for heat —> rock expands —> rock breaks

freeze thaw weathering

water going from the liquid to solid phase

• frost wedging: when water gets into a crack + expands —> forms a wedge

abrasion

physically scraping/ breaking off rock fragments by glaciers, water, wind

stress release weathering

rocks compressed during burial by overlapping rock —> rocks expand if overlying rock is removed

exfoliation

peeling off a large sheet of rock

chemical weathering

chemical decomposition

• different rocks weather at different rates bc of chemical comp + mechanical properties (physical)

• can break down through environmental conditions, time, solute concentrations, microbes

congruent weathering

fully dissolved: concrete dissolution of a mineral

Incongruent weathering

partially dissolved: production of some dissolved product and makes another mineral

how mechanical weathering and chemical weathering work together

mechanical weathering breaks down rock physically —> smaller grains —> more surface area —> more solid/ liquid interactions (potential for chemical weathering)

soil

complex mixture of minerals, water, air, and organic matter capable of supporting life on earth’s terrestrial surface

soil profile

1 dimensional vertical side-view of the soil that shows all of its distinct horizontal layers (soil horizon)

• O Horizon: topmost layer, organic matter like decomposing leaves

• A Horizon: topsoil

• E Horizon: minerals and clay washed away

• B Horizon: subsoil

• C Horizon: Made of broken, partially weathered parent rock.

• R Horizon: Solid bedrock sitting underneath all the other layers

soil horizon

distinct layers of soil that all differ from each other

soil formation process

driven by energy and water

1. input (put into soil)

2. output (erosion)

3. translocations (physical movement of solids and gasses w/ soil)

4. transformations (secondary minerals (chemical) and secondary organic compounds (decomposition))

regolith

loose, unsorted superficial deposits covering solid rock

weathering and climate relationship

• hot and wet = strong chemical weathering (water, higher temp)

• cold and dry = strong mechanical weathering (freeze thaw, glacial flour)

lithifaction

loose sediments cemented together to create a cohesive rock

clastic rocks

made up of broken pieces of older rock

biochemical rocks

biology/ other chemicals cause minerals to precipitate and then be deposited

• ex: shells, organics, salts

3 types of clastic rocks

1. conglomerates: gravel (big grains)

2. sandstones: sand (small grains)

3. mudstones: mud (can’t see grains)

amount of energy needed to move clastic rocks

low energy: mud —> mid energy: sandstone —> high energy: conglomerates

3 main settlement transportation fluids

1. wind

2. water

3. ice

wind as a settlement transportation fluid

• carries fine grained settlements (mud sized)

• only in dry/ arid areas (bc can’t stick to anything wet)

• loess

• can build sand dunes

water as a sediment transportation fluid

• carries vast amt of sediment (sand and mud)

• shallow currents can empty sediment into ocean redistribution

• steeper, fast streams (high energy) —> conglomerates

• rivers that empty into large body of water —> low energy water —> mud deposited

ice as a sediment transport fluid

• one of the most effective ways to push/ erode sediments

• glacial till

loess

silt and clay dust; wind storm

glacial till

huge boulders that glaciers leave behind

sedimentary structures

clues in the rock that indicates the environment that rock was formed in

cross stratification

ripples on stream bed created by current/ wind

• only found in sand dunes and riverbeds

carbonate rocks

• mostly limestone

• 20-25% of sedimentary rocks

• creates importate marine habitats

• driven by biomineralization, microscopic organisms

• coal

• oil shales

oil shales

clay and 15-75% organic material (kerogen)

evaporites

dissolved salts precipitated from water

messinian salinity crisis

restricted water exchange w/ atlantic ocean and straight of gibraltar —> cycles of large evaporite deposits across mediterranean sea

why oceans matter

• climate —> absorbs and transports heat around the world

• recreation

• absorbs carbon dioxide and produces over 50% world’s oxygen

• transportation

• food and medicine

bathymetry

the great variation of the depth of the ocean floor

how there are salinity differences in ocean

• currents

• rivers

• evaporation

• precipitation

• different water temp

thermocline

rapid change in salinity from temp vs depth

stratification

separation of density of the different waters

primary productivity

when primary organisms (algae and marine plants) consume atmospheric carbon dioxide + dissolves in surface ocean —> more carbon dioxide in surface ocean

ocean currents

continuous, recognizable flows in the ocean

• surface currents: upper 100 meters of water

• deep currents: deeper parts of ocean

ekman transport

friction btw wind and surface ocean makes water move 90^o right of wind direction bc of earth’s rotation

ocean gyres

large, slow moving circular ocean currents driven by wind and density gradients

upwelling

where deep water full of nutrients is pulled up to surface for photosynthesis

• happens along western continent boundaries

how to make deep ocean water

• deeper = more dense

  • colder + saltier = more dense

• sea ice —> more dense

  • fresh water leaves behind salt —> salt sinks to bottom —> more dense deep ocean

• mostly in north atlantic

sea ice

ice that forms directly on ocean that makes water more dense

• forms fresh water when cold —> leaves behind salt on surrounding area