Name: Earthquakes 101 Earthquakes can cause the ground to shake and crack apart. Earthquakes can be very powerful, and if they occur in or near areas

where people live, they can make buildings collapse, bridges sway, and roads buckle.

An Alaskan earthquake caused the ground to crack apart.

But not all earthquakes are powerful enough to cause damage. In fact, earthquakes

are happening all the time, on land and in the ocean. Most are so small that people

don't even feel them. An earthquake is the sudden movement of the Earth's crust.

Earthquakes occur along fault lines, cracks in the Earth's crust where tectonic plates

meet. They occur where plates are subducting, spreading, slipping, or colliding. As

the plates grind together, they get stuck and pressure builds up. Finally, the pressure

between the plates is so great that they break loose. Depending on how much

pressure has built up, the ground may tremble slightly or shake forcefully.

This highway in California collapsed during an earthquake.

Scientists describe the intensity of an earthquake using the Richter Scale. It

measures earthquakes on a scale of 1 to 10. People barely feel a magnitude 3

earthquake, and windows might rattle at magnitude 4. A magnitude 6 earthquake is

considered major, causing houses to move and chimneys to fall. The largest

earthquake on record had a magnitude of 9.5.

Why do Earthquakes Happen?

In 1906, the seismologist Henry Reid developed the “elastic rebound theory” to

explain earthquakes. When rocks begin to press against each other, they initially

bend, like a spring, to accommodate the opposing forces. Eventually, when the rocks reach a point where they cannot bend

further, they break. The bent rocks snap back, or rebound, to their original shape. The break is the fault itself, and the shock waves

emanating from the rebound are the earthquake. The shock waves vibrate through the Earth, making it “ring” like a bell.

Mapping Major Recent Earthquakes

On a map you often see lines of latitude (east to west) and lines of longitude (north to south). These lines help us identify specific

places on the Earth. The Equator is a special line of latitude and is 0°. Everything north of it is considered north. Everything south of it is

considered south.

°)

The Prime Meridian is a special line of longitude and is 0°. Everything west of it is considered west. Everything east of it is considered

east.

West East

°)

If we are given information about a location’s longitude and latitude we can identify where it is on a map. For example if you had a

location that was 60° N (60° north of the Equator) and 120° W (120° west of the Prime Meridian) you would have a location in Canada.

The Earth is huge so sometimes we have to estimate a bit because of the scale. If you were asked to find 20° S and 135° E you’d have

to estimate, but it’s definitely in Australia

This is where 60° N and 120° W meet

20° S

is about

here

135° E is about here

20° S and 135° E is about here

Mark locations of some major earthquakes with a dot on the map on the next page. Copy and paste the example dot, draw your own or

go to “insert” then choose “shapes” to put one in yourself. Once all the dots are on the map you’re done.

Recent Major Earthquakes:

Longitude/Latitude Location Year

38° N, 48° E Iran 1962 (Example done) 61° N, 147° W Alaska 1964 12° N, 87° W Nicaragua 1972 15° N, 92° Guatemala 1976 39° N, 118° E China 1976 40° N, 40° E Turkey 1976 25° S, 68° W Argentina 1977 1° N, 78°W Ecuador/Colombia 1979 37° N, 137° E Japan 1983 18° N, 102° W Mexico 1985 41° N, 45° E Armenia 1988 37° N, 122° W California 1989 35° N, 135° E Japan 1995 47° N, 122° E Washington State 2001 29° N, 58° E Iran 2003 35° S, 71° W Chile 2010 18° N, 72° W Haiti 2010 37° N, 140° E Japan 2011 3° N, 95° Indonesia 2012