Ch. 9 Study Guide Answers

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