Chapter 18 Volcanic Activity. Section 18-1 Magma. Objectives: Describe factors that can affect the formation of magma Compare and contrast the different types of magma. Volcanic Eruptions.
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As the flowing magma cools inside of the solid rock, it crystalizes and forms blocks, ribbons or veins of new “intrusive” igneous rock.
Batholiths are the specific name given largest formations of plutons. They are usually found in large mountain ranges. They cut across rock layers.
Laccoliths tend to form near the Earth’s surface where they cause the rock above to push upward in a dome shape.
Sills are intrusions that form parallel to the existing rock, they tend to stay underground and flow like a “spill”.
At the top of a volcano around the vent is a bowl-shaped depression called a crater
Rock fragments thrown into the air during an eruption are called tephra.
The distribution of volcanoes around the world is not random, most occur at plate boundaries.
Plates coming together, this forms the Pacific Ocean “Ring of Fire” and the “Mediterranean Ring” in the Atlantic.