week 7

Earth Differentiation

denser materials sink lighter materials rise - core, mantle, crust, hydrosphere, atmosphere

6371 km

earth's radius is how deep?

Major elements in the earth

iron, oxygen, silicon, magnesium

mantle rock

is the density higher for mantle rock or crustal rock?

seismicity

occurrence of earthquakes in space and time

Earth's interior, not the liquid

s wave paths go through what?

1) time of an earthquake 2) distance from epicenter 3) Richter magnitude of the quake.(as well as information about the interior of the Earth)Amplitude

seismographs are used for...

core-mantle boundary

sharp increase in density, but also sharp decrease in rigidity

Love wave

side-to-side shear motion

earthquake

sudden motion in the Earth caused by abrupt release of accumulated strain energy along a fault plane

earthquake epicenter

the point on Earth's surface directly above the focus

seismology

The study of earthquake waves and the deep interior of Earth

surface and body waves

types of seismic waves?

Mantle Tomography

uses seismic waves to study temperature variations in the mantle based on velocities of seismic waves

Creep Motion

- less dangerous - does not generate a lot of energy or large earthquakes

P waves

- Primary waves - fastest - push/pull motion - travel through solid and liquid

surface waves

- Travel along Earth's surface - Cause most of the damage associated with earthquakes - Do not penetrate the interior - motion restricted to shape of earth

thermal convection

- Warm, less-dense material rises; cooler, denser material sinks. - Hot material is transferred from the interior toward the exterior of the planet. - Segregates material by density

CT Scans

- computed tomography = CT - non-invasive imaging

compositional convection

- light material rises; heavy material sinks - convection in outer core affects growth of inner core

S waves

- secondary waves - slower than P - shearing motion - only travel through solids

body waves

- travel through Earth's interior - two main types: primary (P) and secondary (S)

crust

10-70 km thick Ca, Al, Si, O

inner core

1500 km thick solid iron

outer core

2200 km thick liquid iron

mantle

2800 km thick Mg, Fe, Si, O

main components of rocks in crust

Si, Al, Ca, O

main components of rocks in mantle

Si, Mg, Fe, O

earthquake cycle

The concept that there is a periodic quality about the occurrence of major earthquakes on a given fault zone, with repeated cycles of stress buildup, rupture, and relaxation of stress through smaller aftershocks - not periodic or predictable - stick-slip motion

earthquake focus

The location where the earthquake begins

Elastic Rebound Theory

The theory that continuing stress along a fault results in a buildup of elastic energy in the rocks, which is abruptly released when an earthquake occurs.

Rayleigh wave

goes up and down AND forward - rolling motion - eliptical like

The longer the P-S time gap, the greater the distance between the seismograph and the epicenter

how is the epicenter of an earthquake determined?

plate tectonics

interior structure and convection of the solid mantle is responsible for...?

fault traces

lines that indicate the point where a fault intersects the ground surface

moon materials

made out of iron and lighter matter

fault

planar fracture along which displacement (offset) has occurred

geothermal gradient

rate of change of temperature with depth

path; speed

the actual ______ taken by seismic waves is not straight and the _______ at which they travel is not constant

12 km

the deepest drill is how deep?

3.8 km

the earth's deepest mine is how deep?

solid

the mantle convects even though it is...?

circulation in the earth's interior

thermal convection compositional convection

seismic ray

traces the path of a single point along the wave front and is always perpendicular to the wave front

seismology

we can study earth's interior directly using...?

the abrupt release of energy stored along faults by the build-up of stress

what are earthquakes caused by?

Our atmosphere from solar wind, records plate tectonic motion

what does the magnetic field from the core protect?

a liquid outer core

what does the s wave shadow zone provide evidence for

Hayward fault

what fault runs through Cal's football field

pressure, temperature, and density

what increases toward the center of the earth?

abruptly at boundaries where the rigidity of materials changes - such as the core-mantle boundary

when and where do seismic velocities change?

velocity - mantle rock has higher density than crustal rock; also has higher velocity

when density is higher, what else has to be higher?

extreme pressure and temperature depth

why can't we sample the deep earth?

The velocity that P and S waves travel depends on the density and rigidity of the material they are traveling through

why do waves get refracted?