Earthquakes

Word	Definition
Primary waves	are P-waves. fastest. longitudinal = vibrates back and forth
Secondary waves	are S-waves. slower. transverse = vibrates from side to side.
Earthquake	sudden movement of Earth's crust that releases energy.
Focus	is the origin of an earthquake.
Epicenter	is the place directly above the focus on Earth's surface.
Refraction	P-waves change direction as it enters into a different layer.
Seismograph	a machine that records the earthquake waves.
Seismogram	a recording of earthquake waves.
Origin time	the time when both P-wave and S-wave start to travel.
Travel time	the time for earthquake waves to travel.
Subduction	Two tectonic plates converge. One plate goes underneath another plate.
Seafloor spreading	happens at the mid-ocean ridge where new magma comes out as 2 plates diverge.

Word

Definition

Primary waves

are P-waves. fastest. longitudinal = vibrates back and forth

Secondary waves

are S-waves. slower. transverse = vibrates from side to side.

Earthquake

sudden movement of Earth's crust that releases energy.

Focus

is the origin of an earthquake.

Epicenter

is the place directly above the focus on Earth's surface.

Refraction

P-waves change direction as it enters into a different layer.

Seismograph

a machine that records the earthquake waves.

Seismogram

a recording of earthquake waves.

Origin time

the time when both P-wave and S-wave start to travel.

Travel time

the time for earthquake waves to travel.

Subduction

Two tectonic plates converge. One plate goes underneath another plate.

Seafloor spreading

happens at the mid-ocean ridge where new magma comes out as 2 plates diverge.

Key Things to Know in Earthquakes

P-waves are faster than S-waves.
P-waves travel through solids and liquids while S-waves only go through solids.
Need 3 seismic stations to locate an epicenter.
A S-wave's travel time is longer than P-wave's travel time because S-wave is slower.
A greater time difference between P- and S-waves corresponds to a greater epicenter distance.
A larger epicenter distance requires a greater travel time .
The alternating polarity of bands on one side of the mid-ocean ridge is symmetric to the other side.
Mid-ocean ridge - new earth being created. This is called sea floor spreading.
Trenches - earth being destroyed. This is called subduction zone.
Isostasy: earth's crust in equilibrium (uplift and subsidence).
Energy moves from source to sink: high to low.
Convection currents in the mantle move plates.
Mountains form by uplift, folding and faulting.
Ocean crust is thin and made of basalt.
Continental crust is thick and made of granite.

Example 1

Alternating parallel bands of normal and reversed magnetic polarity are found in the basaltic bedrock on either side of the
(1) Mid-Atlantic Ridge
(2) Yellowstone Hot Spot
(3) San Andreas Fault
(4) Peru-Chile Trench

These bands of magnetic polarity only happens at a mid-ocean ridge where new rocks are formed as magma comes out onto Earth's surface. (1)

Exercises

1. The diagram below shows a laboratory setup. The rubber band holds filter paper across the base of the open tube to hold the soil sample. The tube was placed in the water as shown. The upward movement of water is represented by arrows. The height of the water that moved upward within the soil was measured. Students repeated this procedure using soils with different particle sizes. Results of the experiment are shown in the data table.
exercise Q 5 picture

Results of this experiment lead to the conclusion that
(1) capillarity is greater in soils with larger particles
(2) capillarity is greater in soils with smaller particles
(3) permeability is greater in soils with larger particles
(4) permeability is greater in soils with smaller particles

Earthquakes

Key Words in Earthquakes

Key Things to Know in Earthquakes

Example 1

Exercises