Geology and Seismology: Folds, Faults, Earthquakes, and Streams

folds

bends or wavelike undulations in rock layers formed by deformation

Fold deformation

ductile

ductile deformation

rocks bend without breaking

stressed involved with folds

compressional

axial plane

imaginary plane dividing a fold into two symmetrical halves

limb

sides of a fold; rock layers that slope away from the axial plane

anticline

arch shaped fold with limbs dipping away from the center

oldest rocks are found in the middle of this fold

anticline

syncline

trough shaped fold with limbs dipping toward the center

youngest rocks are in the middle

syncline

monocline

single bend in horizontal rock layers

rock ages vary in the center

monocline

earthquake

ground shaking caused bu sudden release of energy due to movement along faults

cause of earthquakes

slippage along faults

Mainshock

largest earthquake in a series

foreshock

smaller earthquakes that occur before mainshock

aftershock

smaller earthquakes that happen after mainshock

hypocenter (focus)

point inside earth where earthquake begins

epicenter

point inside earths surface directly above the focus

normal fault

divergent boundary (away)

reverse fault

convergent boundary (towards)

megathrust fault

subduction zone (oceanic under continental)

strike slip fault

transform boundary (slides)

intraplate fault

faults that occur within a tectonic plate

seismic waves

vibrations produced by earthquakes

type of seismic waves

body and surface

body waves

p and s waves

p wave

compressional, fastest, travel through solid, liquid, and gas

s wave

shearing, slower, travels through solid only

surface waves

travel along earth's surface and cause the most damage

seismograph

instrument to record earthquake vibrations

moment magnitude scale

Measures energy released by an earthquake.

modified mercalli intensity scale

measures observes damage and human perception

earthquake destructive hazards

ground shaking, liquefaction, landslide, fire, tsunami

liquefaction

soil loses strength and behaves like liquid

tsunami

large ocean wave caused mainly by megathrust faults

earthquake safety

drop, cover, hold on, stay away from window

seismic zones

circum-pacific belt and alpine-himalayan belt

stream

any flowing body of water

river

large stream

drainage basin

land area that drains water into a single stream

separates drainage basin

divide

sediment transport

dissolved, suspended, and bed load

dissolved load

materials carried in a solution

suspended load

fine particles carried within water column

bed load

sand, gravel, and large particles rolled or bounced along the bottom

alluvium

sediment transported by streams

meandering stream

single winding channel

cutbank

zone of erosion

point bar

zone of deposition

oxbow lake

cutoff meander

braided stream

network of channels separated by bars; common with high sediment loads

floodplain

flat area that floods during high water

natural levee

elevated sediment ridges built by repeated floods

flooding

overflow of water onto normally dry land

flash flood

rapid

slow-onset flood

develops gradually

dam-failure flood

caused by breach of a dam

recurrence interval

statistical measure of how often a flood of a given size is likely to occur

flood safety

have an evacuation plan, avoid driving in water, move to higher ground

alpine-himalayan belt

one of earth's major seismic zones stretching from the Mediterranean to Southeast Asia

Circum-Pacific Belt

world's most active earthquake and volcanic zone surrounding Pacific Ocean

Divide

highland or ridge that separates drainage basins

watershed

area of land where water drains into a single stream of river

fault

a fracture in Earth's crust where movement occurred

intraplate earthquakes

earthquakes that occur away from plate boundaries

how to protect yourself during a flood

avoid water, find high ground