igneous landforms and geothermal activ

geysers

Geysers are also created by water that is heated beneath the Earths surface. The water may become superheated by magma. It becomes trapped in a narrow passageway. The heat and pressure build as more water is added. When the pressure is too much, the superheated water bursts out onto the surface. This is a geyser. There are only a few areas in the world where the conditions are right for the formation of geysers. Only about 1,000 geysers exist worldwide. About half of them are in the United States. The most famous geyser is Old Faithful at Yellowstone National Park (Figure 8.23). It is rare for a geyser to erupt so regularly, which is why Old Faithful is famous.

hot springs

When hot water gently rises to the surface, it creates a hot spring. A hot spring forms where a crack in the Earth allows water to reach the surface after being heated underground. Many hot springs are used by people as natural hot tubs. Some people believe that hot springs can cure illnesses. Hot springs are found all over the world, even in Antarctica!

hot springs and geysers

Water works its way through porous rocks or soil. Sometimes this water is heated by nearby magma. If the water makes its way to the surface, it forms a hot spring or a geyser.

landforms from lava

Extrusive igneous rocks cool at the surface. Volcanoes are one type of feature that forms from extrusive rocks. Several other interesting landforms are also extrusive features. Intrusive igneous rocks cool below the surface. These rocks do not always remain hidden. Rocks that formed in the crust are exposed when the rock and sediment that covers them is eroded away.

landforms from magma

Magma that cools underground forms intrusions (Figure 8.22). Intrusions become land formations if they are exposed at the surface by erosion.

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new land

New land is created in volcanic eruptions. The Hawaiian Islands are shield volcanoes. These volcanoes formed from fluid lava (Figure 8.21). The island grows as lava is added on the coast. New land may also emerge from lava that erupts from beneath the water. This is one way that new land is created.

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lava plateaus

A lava plateau is made of a large amount of fluid lava. The lava flows over a large area and cools. This creates a large, flat surface of igneous rock. Lava plateaus may be huge. The Columbia Plateau covers over 161,000 square kilometers (63,000 square miles). It makes up parts of the states of Washington, Oregon, and Idaho. Thin, fluid lava created the rock that makes up the entire ocean floor. This is from multiple eruptions from vents at the mid-ocean ridge. While not exactly a lava plateau, its interesting to think about so much lava!

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lava domes

When lava is thick, it flows slowly. If thick lava makes it to the surface, it cannot flow far from the vent. It often stays right in the middle of a crater at the top of a volcano. Here the lava creates a large, round lava dome (Figure

instructional diagrams

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questions

When lava is thick it

a. travels far from vents.

b. forms a caldera.

c. flows rapidly.

-->  d. none of the above

Lava that flows from vents at mid-ocean ridges

a. forms composite volcanoes.

b. creates lava plateaus.

c. creates lava domes.

-->  d. is thin and runny.

Examples of lava plateaus include the

a. ocean basins.

-->  b. Columbia Plateau.

c. Hawaiian Islands.

d. two of the above

An intrusion forms when

a. a volcano erupts.

-->  b. magma cools underground.

c. lava hardens at the surface.

d. lava is very thin.

Which statement about hot springs is false?

-->  a. They are very rare.

b. They are found in Antarctica.

c. They are used as natural hot tubs.

d. They are thought to cure illnesses.

A geyser forms when underground water is

a. superheated.

b. under pressure.

c. trapped in a narrow passage.

-->  d. all of the above

Which statement about geysers is false?

a. There are only about 1000 geysers in the world.

b. About half the worlds geysers are in the U.S.

c. The water in geysers is heated by magma.

-->  d. All geysers erupt on a regular schedule.

hot water that seeps out of a crack at the surface

a. extrusive igneous rock

b. intrusive igneous rock

c. lava dome

d. lava plateau

-->  e. hot spring

f. geyser

igneous rock formation that results when lava cools in the middle of a volcanic crater

a. extrusive igneous rock

b. intrusive igneous rock

-->  c. lava dome

d. lava plateau

e. hot spring

f. geyser

hot water under pressure that forcefully erupts out of the surface

a. extrusive igneous rock

b. intrusive igneous rock

c. lava dome

d. lava plateau

e. hot spring

-->  f. geyser

type of igneous rock that forms when magma cools below Earths surface

a. extrusive igneous rock

-->  b. intrusive igneous rock

c. lava dome

d. lava plateau

e. hot spring

f. geyser

type of igneous rock that forms when lava cools on Earths surface

-->  a. extrusive igneous rock

b. intrusive igneous rock

c. lava dome

d. lava plateau

e. hot spring

f. geyser

flat surface of igneous rock that forms when thin lava flows over a large area

a. extrusive igneous rock

b. intrusive igneous rock

c. lava dome

-->  d. lava plateau

e. hot spring

f. geyser

Intrusive igneous rocks are never visible on Earths surface.

a. true

-->  b. false

A lava dome is any mountain that forms from lava.

a. true

-->  b. false

The lava that forms a lava dome is thin and runny.

a. true

-->  b. false

A lava plateau forms when a volcano produces very little lava.

a. true

-->  b. false

Lava from shield volcanoes created the Hawaiian Islands.

-->  a. true

b. false

Intrusions form on the surface and later are buried by sediments.

a. true

-->  b. false

The water in hot springs is heated by magma.

-->  a. true

b. false

diagram questions

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