Science - Grade 3 - Lesson 1: How Do Volcanoes and Earthquakes Change the Earth?


Terms in this set (...)

What is a volcano?
A volcano is a type of mountain that has an opening at the top through which lava, ash, or other types of volcanic rock flow.
What is a vent?
A vent is an opening in a volcano.
What is the earth's crust?
The earth's crust is the top, outer layer of the earth.
What does "erupt" mean?
Erupt means to burst out.

An eruption can be very strong or rather gentle.
The force of a volcano eruption depends on what?
The force with which a volcano erupts depends on the mixture of magma, water, and gases in the lava.

1. Magma with high gas and water content tends to erupt more violently.

2. Magma with low gas and water content tends to erupt rather gently.
How does magma form?
The inside of the earth is hot--so hot, that some rocks melt and become a thick, flowing material called magma.
How do volcanoes form?
1. Magma rises from deep inside the earth. It gathers in a magma chamber.

2. Magma pushes upward through cracks in the earth.

3. Lava erupts from the volcano.

4. Lava builds up outside the volcano. It cools and hardens. A mountain forms.
What would a gentle eruption be like?
Magma with low gas and water content tends to erupt rather gently. Lava pours out of the vent and over the sides of the volcano like heavy syrup. The volcanoes in Hawaii often erupt like this.
What would a strong eruption be like?
Magma with a high gas and water content tends to erupt more violently. Lava, ash, or other types of volcanic rock explode out of the volcano.
What is an earthquake?
An earthquake is a shaking or sliding of the surface of the earth. During an earthquake the land may move up, down, or sideways.
How do earthquakes change the earth's surface?
The earth's surface has many cracks. During an earthquake, blocks of rock (or plates) beneath the earth's surface move and form new cracks or faults.
What are faults?
Faults are large cracks in the earth's crust.
What is a seismograph?
A seismograph is an instrument that measures movements within the earth. They detect the small tremors that can proceed (come before) volcanic eruptions?
How could you stay safe during an earthquake?
1. Have an earthquake kit.

2. If you are inside, stay away from objects that could shatter or fall on you.

3. If you are outside, stay away from structures that could collapse on you.

4. Duck, Cover, Hold--take cover under a desk or strong table; hold onto the table and move with it. Stay in this position until the ground stops shaking and it is safe to move.
What items would you find in an earthquake kit?
An earthquake kit should contain flashlights, batteries, a fire extinguisher, a radio, a first-aid kit, water, canned food, and warm clothes.
How are landforms formed?
Landforms are shaped by natural forces. Natural forces on the earths surface that shape the land are water, wind, or ice (glaciers). Movement of magma or movements of the earth's plates are also natural forces that shape the land but come from within the earth.
How do volcanoes change the Earth's surface?
1. Lava cools into solid rock.

2. As more and more lava builds up on the earth's surface a mountain or volcano forms.

3. A volcano might erupt many times. Each time a volcano erupts, more lava spreads over the volcano.

4. Volcanoes can change the earth's surface quickly.

5. Some volcanoes form under the ocean--some islands formed this way--Hawaii, Japan, and Surtsey (near Iceland) are some examples.
What is lava?
Lava is hot, melted rock that comes out of a volcano.
What is magma?
Magma is hot, melted rock and gases deep INSIDE the earth.
How do scientists study volcanoes and earthquakes?
Scientists use seismographs, tilt meters, and satellites to study volcanoes and earthquakes. Scientists know that earthquakes happen during, or just before, the eruption of a volcano; and, that volcanoes and earthquakes happen in the same general areas of the world.
What is a tilt meter?
A tilt meter measures the tilting of the ground. Tilt meters are placed on the flanks (sides of) of volcanoes to show when rising magma is moving before an eruption.
What does the Richter scale do?
The Richter scale measures the magnitude of earthquakes. The more powerful earthquakes have a height magnitude.
What are shock waves?
Shock waves are also know as seismic waves. Shock waves spread through the rock in all directions and can be felt far away from the center of the earthquake.