How the Earth Works Exam 2

continental jigsaw, fossils match across the seas, rock types and structures match, ancient climates

Continental drift evidence

Pangea

supercontinent

Alfred Wegner

creator of continental drift hypothesis

lithosphere

strong, rigid layer, made of broken plates

crust and uppermost solid mantle

oceanic lithosphere

basalt, thin, but thicker with age

oceanic

mafic crust

continental lithosphere

granitic, thicker

continental

felsic crust

asthenosphere

upper mantle, weak, hot and pressure, able to flow, allows outer sphere to move

mesosphere

lower mantle, pressure counteracts temperature to create strong rocks

outer core

liquid layer of the core that generates earth’s magnetic field

inner core

solid (iron) layer of the core because of immense pressure

tectonic plates

Large sections of the Earth's lithosphere that move and interact with each other, responsible for earthquakes, volcanic activity, and the formation of mountains

plate boundary

where tectonic plates meet and interact, causing geological activity

divergent boundary

constructive, plates moving apart

oceanic divergent boundary

causes seafloor spreading

seafloor spreading

Process where new oceanic crust is formed at mid-ocean ridges and spreads outward, pushing older crust aside. Driven by convection currents in the mantle.

mid-ocean ridges

Underwater mountain ranges that form at divergent plate boundaries. They have volcanic activity and the upwelling of molten rock from the Earth's mantle.

5

The sea floor moves about __ cm per year.

180 million

None of the ocean floor exceeds __ years old.

slower

The __ the spreading of magma, the more even and smooth the surface becomes.

continental divergent boundary

causes continental rifting

convergent boundary

destructive, plates moving towards each other

subduction zone

where one plate bends and sinks down into the asthenosphere beneath another plate

oceanic

Which crust is denser: oceanic or continental?

deep-ocean trenches

form at oceanic subduction zones

older

The __ the crust, the steeper the angle of subduction.

younger

The __ the crust, the warmer and less dense it will be.

downgoing plate

plate being subducted

overriding plate

plate going overtop

oceanic; continental

The __ plate always subducts under the __ plate.

accretionary prism

A wedge-shaped mass of sediment and rock scraped off the top of a downgoing plate that accumulates at the boundary

partial melting

when the minerals with the lowest melting temperatures inside a rock melt first while the other minerals remain solid

water

Subduction zones allow __ to be brought into the mantle, which heats up, allowing the mantle to melt and magma to form.

oceanic-oceanic convergent boundary

creates volcanic island arcs

back-arc basin

depression formed by subduction zones behind a volcanic island arc

continental-continental convergence

Type of convergence where neither plate can subduct, causing a collision and forming a mountain belt

transform boundary

neither constructive nor destructive, plates sliding past each other

San Andres Fault

an active transform fault in the United States that produces frequent earthquakes

offset of mid-ocean ridge

series of transform faults that are present along a ridge axis causes this

continental margin

edges of continents where they meet the ocean

active continental margin

continental margin where there is a plate boundary

passive continental margin

continental margin where there is no plate boundary

hot spots

record the movement of plates over time through the formation of volcano chains

seamount

extinct volcanoes that sink below the sea level

Earthquake

a vibration caused by the sudden breaking or frictional sliding of rock in the Earth

fault

a fracture on which one body of rock slides past another

focus/hypocenter

location where a fault slips during an earthquake underground

epicenter

point above ground directly above the focus of an earthquake

fault trace

The visible line on the Earth's surface where a fault is exposed due to movement of tectonic plates

fault creep

fault displacement without large earthquakes, movement that occurs slowly and relatively smoothly

rapid release of elastic energy stored in rock that has been subjected to great stress

Why do Earthquakes occur?

Elastic rebound

springing back of a rock to its original shape once an earthquake has occured

footwall

rock mass that lies below the fault plane

hanging wall

rock mass above the fault plane

normal fault

hanging wall moves down, divergent plate

extension

a normal fault is caused by __

reverse/thrust fault

hanging wall moves up, convergent

compression

thrust and reverse faults are caused by __

steeper

the reverse fault has a __ angle than the thrust fault

transform fault

horizontal movement

shear

transform faults are caused by

right or left lateral

directions of transform fault movement

look at opposite plate from the other side

how to determine transform fault movement

seismic waves

waves that travel through the crust generated by earthquakes

surface waves

seismic waves that travel on the surface of the Earth

greatest; slowest

surface waves cause the __ damage and have the __ velocity

Rayleigh/r-wave

surface wave that creates an up and down motion

Love/l-wave

surface wave that creates a back and forth motion

body waves

seismic waves that travel within the Earth’s interior

primary/p-wave

body wave that can travel through any substance

secondary/s-wave

body wave that can only travel through solids

compression; shear

p-waves use __ to make an push/pull motion, while s-waves use __ to make a up/down motion

p-waves, s-waves, surface waves

seismic waves from fastest to slowest

arrival times of different waves

What do seismographs use to determine the distance to an earthquake’s epicenter?

foundation conditions, building standards, population density

Factors influencing the damage caused by an Earthquake

less

hard igneous rock will have __ ground shaking than silt and mud during an earthquake

liquefaction

Earthquakes can cause __ which is the process where water mixes with sand and clay to make a slurry

foundation damage

Earthquakes can cause __ where the shaking causes the soil and sand in the ground to loose cohesion so that the particles stop touching, making the ground and foundation unstable. Mass wasting also occurs.

tsunamis

Earthquakes can cause __ where large waves surge on the shore.

shadow zone

an area inside the Earth where seismic waves do not reach because of the bending and reflection of waves by the Earth's core, which helps scientists understand the structure and composition of the Earth's interior

Temperature, magma composition, dissolved gases

How violently or gently a volcano erupts is determined by these three things

magma chamber

Where the magma is held inside the volcano

conduit

the pipe that connects the magma chamber to the opening

higher

a material __ in viscosity will flow with greater difficulty

lower

Mafic magmas have __ viscosity than felsic ones

basaltic lava

example of a mafic magma, which is found on the seafloor

less

Hotter magmas are __ viscous

increase

dissolved gases (volatiles) __ the fluidity of magma

most

felsic magma has the __ silica and gas content, so it is also has the __ viscosity

rhyolitic lava

Example of a felsic magma

andesitic lava

example of an intermediate magma

50-60; 1-6

magmas range from __ to __ percent in silica content, and __ to __ percent in gas content

Pahoehoe

basaltic lava that forms relatively smoothly with some wrinkles

Aa

basaltic lava that flows slower than Pahoehoe and has rough and jagged edges

lava tubes

tunnel underneath hardened lava where lava still flows

effusive eruption

type of eruption where the magma flows gently

explosive eruption

violent eruption filled with pyroclastic material

fissure eruption

eruption from a linear tear in Earth’s surface, creating a curtain of lava and stair-step topography

shield volcanoes

volcanoes that have effusive eruptions