Ch. 9 Study Guide Answers

2011

• A vent or fissure in the Earth’s surface through which magma and gases are expelled is called

• A Volcano

• What would you expect to see during a non-explosive eruption?

• Huge lava flows.

• Molten rock deep underground often gathers in a

• Magma Chamber

• Which type of lava flows most like dripping wax?

• Pahoehoe

• Lava that is very runny probably • has a low silica content

• If the water content of magma is high,• an explosive eruption is more likely

• When you talk about the viscosity of lava, you are talking about

• how the lava flows (thickness).

• Most active volcanoes form• (80%) where tectonic plates collide

• Cool, stiff lava that forms in jumbled heaps of sharp chunks near the vent is called

• Blocky Lava

• Which type of pyroclastic material gets its name from a word that means “little stones”?

• Lapilli.

• The pyroclastic material that can reach the upper atmosphere and circle the Earth for years is

• Volcanic Ash.

• Pyroclastic material forms when• magma explodes from a volcano and hardens

in the air.

• Describe a possible climate change caused by a volcanic eruption?

• Volcanic Ash high in the atmosphere could block sunlight, causing (regions of earths) temperatures to drop.

• Where are volcanoes most likely to form?• Along plate boundaries

• Large blobs of magma that harden in the air are called

• Volcanic Bombs.

• A large depression that forms when the magma chamber partially empties is a

• Caldera.

• The three main types of volcanoes are• Shield Volcano, Cinder Cone Volcano, and

Composite Volcano.

• The depression created when the roof of a magma chamber collapses is called a

• Caldera

• Rock begins to melt when (what happens) • temperature on the rock increases and

pressure decreases

• Most active volcanoes form• where tectonic plates collide

• When an oceanic plate collides with a continental plate, the oceanic plate is usually sub-ducted because

• the oceanic plate is denser and thinner than the continental crust.

• A cinder cone volcano• has steep slopes

• The volcanoes of Hawaii and other places far from tectonic plate boundaries are known as

• Hot Spots

• Which category of volcano is most likely to erupt in the near future?

• An active volcano

• An active volcano• is currently erupting or show signs of

erupting. In the near future.

• What would you expect to see during a non-explosive eruption?

• Calm lava flows

• Pillow lava is• formed when lava erupts under water

• Lava with a high viscosity• is thick like pudding

• What would you expect after an explosive eruption?

• Darkened Skies.

• A shield volcano • has gently sloping sides

• A combination of explosive and non-explosive eruptions will create a

• composite volcano