NGS Forces that Shape the Earth Sec. 2: Earthquakes

What is an earthquake?

• A large wave in the ocean

• A sudden change in weather patterns

• A vibration in the ground resulting from movement along faults

• A vibration in the ground caused by volcanic eruptions

Answer explanation

Okay, imagine the Earth's crust, the outside layer like the peel of an orange, is actually broken into giant puzzle pieces called tectonic plates. These plates are always moving, super slowly, like snails.

Sometimes, these plates get stuck on each other because they're rough, like trying to slide sandpaper against sandpaper. They build up a lot of pressure, kind of like when you stretch a rubber band too far.

When the pressure gets too much, SNAP! The plates suddenly slip and move past each other. This sudden release of energy sends out vibrations, like ripples in a pond when you throw a rock in. These vibrations are what we feel as an earthquake.

So, the answer is A vibration in the ground resulting from movement along faults. Faults are the cracks where the plates move. It's not a wave in the ocean, a weather change, or just from volcanoes (though volcanoes can cause earthquakes too). It's all about those giant plates moving and getting stuck!

What happened in San Francisco in 1906?

• A tsunami flooded the streets

• A severe hurricane struck the city

• A large volcanic eruption occurred

• A massive earthquake hit and devastated the area

What are tectonic plates?

• Types of rocks found underground

• Layers of the atmosphere

• Sections of Earth's crust that are constantly in motion

• Large bodies of water

What is a fault?

• A deep ocean trench

• A type of rock

• A large mountain range

• A break in Earth's crust where plates meet

Which fault is the most widely known?

• The San Andreas Fault

• The Hayward Fault

• The Cascadia Fault

• The New Madrid Fault

What is a normal fault?

• A fault where rocks are pulled apart along a divergent boundary

• A fault where rocks move vertically

• A fault where rocks are pushed together

• A fault where rocks move horizontally

What is a reverse fault?

• A fault where rocks are pushed together

• A fault where rocks move down

• A fault where rocks are pulled apart

• A fault where rocks move horizontally

What is a strike-slip fault?

• A fault where rocks move vertically

• A fault where rocks slide horizontally past each other

• A fault where rocks are pushed together

• A fault where rocks are pulled apart

What is the focus of an earthquake?

• The location of the largest aftershock

• The area where the most damage occurs

• The point beneath Earth's surface where rock breaks

• The point on the surface directly above the epicenter

What is the epicenter of an earthquake?

• The point beneath Earth's surface where rock breaks

• The point on the surface directly above the focus

• The location of the smallest aftershock

• The area where the least damage occurs