Volcanic Landforms - Guide For Reading (Page 3 of 4) in pdf

Volcanic Landforms - Guide For Reading Page 3

Over time, the hard surface of a lava flow breaks down to form

soil. Some volcanic soils are among the most fertile soils in the

world. People have settled close to volcanoes to take advantage of

the fertile soil. This soil contains potassium, phosphorus, and

other substances plants need.

Sometimes magma rises upward through cracks in the crust but

does not reach Earth’s surface. The magma cools and hardens into

rock beneath the surface.

Features formed by magma include:

1. volcanic necks- A volcanic neck forms when magma

hardens in a volcano’s pipe. The softer rock around the

pipe wears away, exposing the hard rock of the volcanic

neck. Ex. Ship Rock, New Mexico

1. dikes- forms when magma forces itself across rock layers

and hardens.

2. sills- forms when magma squeezes between layers of rock

and hardens. Ex. Palisades, NY & NJ

3. batholiths- When a large body of magma cools inside the

crust, a mass of rock called a batholith forms. This forms

the core of many mountain ranges. Ex. Half Dome in

Yosemite National Park.

4. dome mountains- Smaller bodies of hardened magma can

form dome mountains. A Dome mountain forms when

uplifts pushes a batholith or smaller body of hardened magma

towards the surface. The hardened magma forces the layer of

rock to bend upward into a dome shape. Eventually the rock

above the dome mountain wears away leaving it exposed.

Ex. Black Hills, South Dakota.

Volcanic Landforms - Guide For Reading Page 3