Volcanoes - Geology Worksheet (Page 3 of 4) in pdf

Volcanoes - Geology Worksheet Page 3

Physical Geology 101

Explosive eruptions results in huge volumes of pyroclastic material and gases being forced up into the

atmosphere in the shape of a huge column called a ______________________.

How high can these columns reach? ________________

Examples: ______________________ and _______________________.

When the pyroclastic material first gets ejected sideways from the volcano, the type of eruption is called a

_____________________ (happened at Mt. St. Helens in 1980).

Sometimes, volcanic material can rush down the slopes of the volcano just like an avalanche, and is

called a _________________________. It contains extremely hot bits of semi-molten rock, called

___________, as well as huge volumes of poisonous gases.

What are the three types of tephra (from biggest to smallest particles)?

______________________________

•

______________________________

•

______________________________

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The lava from explosive eruptions is silica-rich and very viscous so it doesn’t flow far. Along with pyroclastic

flows, it builds up a multilayered, steep-sided volcano called a:

__________________________ ; also called a _____________________________

Examples of stratovolcanoes: ___________________ and _____________________

Volcanic Features

There are a number of types of features on Earth that formed through volcanic processes.

Cinder Cones

Cinder cones are built from blobs of congealed lava and lapilli size pyroclastic material ejected from a volcanic

vent that fall to the ground as cinders or clinkers. This material collects in a heap around the vent, forming a

circular or oval cone. Most cinder cones have a bowl-shaped crater at the summit and rarely rise more than a

thousand feet or so above their surroundings. They form due to a single, short-lived eruptive event.

Example from Idaho: ________________________________

Craters and Calderas

A crater is a funnel-shaped depression that exists at the top of most volcanoes.

What is a caldera? _______________________________________________________

Example of a caldera in the Cascades: ______________________________

Volcanoes - Geology Worksheet Page 3