# earth science test 8 Flashcards

1
Q

what is an earthquake

A

the breaking of and movement of rocks within the lithosphere.

2
Q

what are faults

A

faults are fractures in earht where movement has occurred.

3
Q

what is focus

A

the point in earth where the energy is released and most damage occurs

4
Q

how much ditance is most foci at from earths surface

A

65km some can be 700km

5
Q

what is epicenter

A

the point on earths surface directly above the earthquake focus

6
Q

when did elastic rebound start

A

after the 1906 san fransisco earthquake

7
Q

how do earthquakes form

A

when rock that have been subject to great forces reach their limit and burst . Releasing the remaining energy as seismic waves.

8
Q

what are the three types of rorces that act on rock

A

Tension, sheering, and compression

9
Q

tension

A

force that pulls rocks apart. middle becomes thinner like gum

10
Q

compression

A

force that squeezes rocks together until it folds or breaks

11
Q

sheering

A

force that causes rocks on either side of fault to slide past each other this can cause rock to break slip apart or change shape

12
Q

what is elastic deformation

A

if you take an elastic and stretch it, it will bend and stretch according to the force applied

13
Q

what are examples where elastic energy is stored

A

when you stretch rubber band or compress a spring

14
Q

what is elastic rebound

A

when the force is released it returns to original shape like a stick. But if in too much stress it will stayed destroyed.

15
Q

what are the two types of seismic waves

A

body waves, and surface waves

16
Q

what are body waves

A

they carry energy away from the focus through earths interior to surface consists of P and S waves

17
Q

Surface waves

A

they travel at the surface

18
Q

describe P wave
How does crust move

A

they move through earth causing particles in rocks to move back and forth in the same direction the wave is moving.

19
Q

what can P waves move through? what do they cause ground bulding to so

A

solids liquids and gases. Buckle and fracture

20
Q

what are S waves
HOw does crust move

A

they move through earth by causing particles in rocks to move at right angles to the direction of the wave. Crust moves side to side and up and down.

21
Q

at what speed do primary waves move compared to S waves

A

twice as fast.

22
Q

what can S waves travel through

A

Only Solids.

23
Q

What are surface waves

A

waves that travel outward from the epicenter on the surfaceo of the earth> they move by going in a elliptical motion

24
Q

What causes things in an earthquake to fall

A

waves

25
Q

what is the slowest type of wave

A

surface waves

26
Q

what records seismic waves

A

seismograph

27
Q

How does a seismograph work

A

A pen hangs from the weight, and a rotating drum with paper sits below it on the base. When the earth shakes from an earthquake, the drum rotates, and the weighted pen moves back and forth due to the motion of seismic waves. The pen records the movement on the drum.

28
Q

What does amplitude say about the size of an earthquake

A

The larger the amplitude (height of lines) the larger the size of the earthquake.

29
Q

what waves produces the largest disturbance of a seismograph

A

surface waves

30
Q

what is seismic shaking

A

the ground vibrations produces by seismic waves

31
Q

what happens to brick and wood building during seismic shaking

A

Brick buildings may collapse, and wood framed buildings may remain intact but could be jolted off their foundations can also damage or destroy bridges.

32
Q

what does the Richter moment magnitude and Merali scale do?

A

The Richter and moment magnitude measure earthquake magnitude. And the Mercalli scale is based on earthquake intensity

33
Q

how can earthquake damage and loss of life be reduced?

A

determining earthquake risk to area, building earthquake resisitant structures, and following eartquake safety procedures

34
Q

what are the layers the earth can be divided into based on physical properties

A

lithosphere, asthenosphere, upper mantle, lower mantle, outer core, Inner core.

35
Q

earths layerd structure key 3

A

during the twentieth century studies of the paths of P and S waves through earth help scientists to establish the boundaries of earths layers and determine that the outer core is liquid.

36
Q

what is liquefication

A

happens when wet doil that is solid most of the time acts more like a liquid when it is shaken during an earthquake.

37
Q

If you live on the coast what sometime follows earthquakes

A

tsunamis

38
Q

where do most earthquakes occur

A

at plate boundaries/pacific ocean

39
Q

How do you assess earthquaek risk

A

By plotting the distribution of earthquakes on a map to determine a pattern.

40
Q

what are some seismic safe designs

A

Bridges with rubber band holding them. Gas lines with flexible pipes and auto stop. Wood framed houses built on solid ground reinforced and bolted to the ground.

41
Q

what two main type of evidence geologists use to learn about earth’s interior.

A

Direct evidence from rock cycles, and Indirect evidence of seismic waves

42
Q

What are the three major layers of earth

A

mantle, core, and crust.

43
Q

what is the density of crust compared to age

A

180 million=3.0g/cm
4billion=2.7gcm

44
Q

what is crust

A

the top layer of the earth’s surface and the thinnest one.consists of granite rock lkebasalt and gabbro.

45
Q

what is mantle

A

The layer under the crust. It begins near 40km beneath the surface. A solid layer of very hot rock, that is nearly 3000km thick.

46
Q

what is core

A

The core is the inner most layer. about 3480km thick. The center is very hot and contains lots of iron rich materials. The core has extreme pressyre and a density of 13g/cm

47
Q

what is the lithosphere

A

A combination of the uppermost mantle layer and crust. cool layer

48
Q

What is the asthenosphere

A

The layer below the asthenosphere this material is hotter and under increasing pressure this layer is less rigid than the layer above it making it somewhat soft.

49
Q

what is the lower mantle

A

a layer beneath the asthenosphere, it is a solid layer thatextends all the way to earths core.

50
Q

outer core

A

The liquid outer core is above the solid inner core. the flow of metallic iron generates earths magnetic fields.I

51
Q

Inner core

A

The cores center has a radius of 122okm. even though is is very hot it is a solid due to pressure and very dense. SO much so that molecules cant spread and become liquids.