Earthquakes and Volcanoes!

What Did You Learn about Earthquakes?• Shallow earthquakes are associated with… Both!

• Shallow earthquakes are found on the boundary!

Convergent!• Deep earthquakes are found behind the boundary!

• Deep earthquakes are associated with…

Earthquakes Everywhere!

• As the plates try to move, they get stuck on each other. • Stress builds up.

When the stress exceeds the strength of the rock, it will break,

causing energy to be released.

• Seismic waves spread out from the point of failure.

• The point on Earth’s surface directly above the focus is known as the epicenter.

• Earthquakes are natural vibrations of the ground caused by movement along faults.

Measuring Earthquakes• The magnitude of an earthquake is

often measured using the Richter Scale.

• Measures the amount of energy released during an earthquake using a logarithmic scale.

• The intensity of an earthquake is measured using the Modified Mercalli Scale.

• Measures the amount of damaged caused by an earthquake.

• The higher the Roman numeral, the worse the damage.

Tsunamis!• When movement along plate boundaries has a vertical component,

water is displaced forming a tsunami. • Volcanic activity cause tsunamis when the eruption causes a sudden

displacement of water.

• Unlike water waves where the particles just oscillate and the energy is moved, in a tsunami both the energy and the water move with the wave.

Tsunamis are barely noticeable in the open ocean but grow to great heights when they reach land!

Tsunami Impacts• Ecological Results

• Damages coral reefs and coastal habitats.

• Changes salinity of coastal habitats.

• More vulnerable to erosion makes soil less fertile.

What Did You Learn about Volcanoes?• Volcanoes are associated with… Convergent!

• They are found behind the boundary!

Exceptions to The Rule• Hot spots are unusually hot regions of the Earth’s mantle where

high-temperature plumes of magma rise toward the surface. • Magma melts through the crust to form volcanoes on the surface.

• Current theory is that these hot spots are stationary.

• As plate moves, a chain of volcanoes forms.

• Older volcanoes become extinct and will eventually weather away until they become seamounts.

Direction of plate motion is toward the oldest volcano!

Here’s A Song About It!

Meet The Newest Island! Benefits of Hot Spots• Because hot spots are stationary, we can use them to

calculate the speed and direction of a plate.

Let’s Give it A Try with Hawaii!