Unit 4 Dynamic Earth Processes Volcanoes Earthquakes Earth

Unit 4 Dynamic Earth Processes Volcanoes & Earthquakes Earth Sci 3 d Students know why and how earthquakes occur and the scales used to measure their intensity and magnitude Earth Sci 3 e Students know there are 2 kinds of volcanoes: one kind with violent eruptions producing steep slopes and the other kind with voluminous lava flows producing gentle slopes

Volcano • What is it? – A hill or mountain formed when molten rock (magma) comes to Earth’s surface • Magma reaching the surface is called lava

2 Types of Volcanoes • 1. Explosive Eruptions • 2. Non-explosive Eruptions • The silica content of magma helps determine whether the volcanic eruption is explosive or quiet. – Silica is the material formed from silicon & oxygen

Explosive Eruption

Explosive Eruption Volcano • 1. Cinder Cone Volcano – Has steep slope – Build from various materials: • Ash • Cinders • Glass • Lava fragments • Rocks

Explosive Eruption Volcano • 2. Composite Volcano – Most common type – Has steep slope – Explodes both lava & ash – Has alternating layers of lava, ash & mud

Composite Volcano

Non-Explosive Eruption

Non-Explosive Eruption Volcano • Shield Volcano – Built from layers of basaltic lava • Basalt: dark, fine-grained volcanic rock – Not very steep; gentle slopes – Ex: Hawaiian Islands

What causes volcanoes? • The formation of magma – Mantle rock melts when the temperature increases or the pressure decreases

What causes volcanoes? • Where do volcanoes form? – Tectonic Plate Boundaries!!!! Ring of Fire

What causes volcanoes?

What causes volcanoes? • Hot Spots

Earthquake

Earthquake • Why & How it occurs – Earth’s crust movement causes the stresses applied – These stresses can cause rocks to bend and stretch – Eventually rocks will break away from one another • Area in which the rocks break and move is called a fault • Vibrations produced is called an earthquake

Measuring Earthquakes • Seismology – Use instruments called seismographs – Record seismic waves – The height (amplitude) of the lines are used to measure the energy released from the earthquake called the magnitude • Magnitude – Usually determines the strength of the break – Is measured using the Richter scale

Seismograph

Tsunami • Caused by the movement of the ocean floor • An earthquake in a subduction zone can cause tsunami • When the stress reached the point where the overlying plate could no longer bend without breaking, it snapped and jerked upward.

Tsunami

Videos • Volcano – http: //video. nationalgeographic. com/video/player/environment/env ironment-natural-disasters/volcanoes-101. html • Earthquake – http: //video. nationalgeographic. com/video/play er/environment-naturaldisasters/earthquake-101. html • Tsunami – http: //www. youtube. com/watch? v=w 3 Ad. Fjkl. R 50