Visualizing Environmental Science

Plate Tectonics and the Rock Cycle 301

PROCESS DIAGRAM

Magma Sedimentary

rock

Metamorphic

rock

Cooling and

solidification

Weathering

and erosion,

transport and

deposition,

Heating,pressure, and compaction

and chemical

action

Heating

and melting Heating,

pressure, and

chemical action

Basalt columns are a

type of igneous rock

formed by the cooling

of magma.

Quartzite is a

metamorphic rock

derived from

sandstone.

Sandstone is a type

of sedimentary rock.

Lava is magma that

reaches the surface

through a volcanic vent.

1

2

3

4

Igneous

rock

David Edwards/NG Image Collection

Raul Touzon/NG Image Collection

Taylor S. Kennedy/NG Image Collection

© Phil Degginger / Alamy

Rocks do not remain in their original

form forever. This highly simplified

diagram shows how rock cycles from

one form to another.

/…iÊÀœVŽÊVÞViÊUʈ}ÕÀiÊ£Ó°{

✓✓THE PLANNER

What happens to an

igneous rock as it moves slowly through

the rock cycle?

Think Critically

best prepared of all nations when it comes to earthquake

disasters. Japan lies on a seismically active junction of sev-

eral tectonic plates. (See Chapter 17 for a discussion of

damage to Japan’s nuclear power plants from the quake.)

The Rock Cycle

Rocks, which are aggregates of one or more minerals, fall

into three categories, based on how they formed: igneous,

sedimentary, and metamorphic.

Igneous rocks form when magma

rises from the mantle and cools.

Sedimentary rocks form when

small fragments of weathered,

eroded rocks (or marine organ-

isms) are deposited, compacted, and cemented together.

Metamorphic rocks form when intense heat and pressure

alter igneous, sedimentary, or other meta morphic rocks.

Earth’s internal structure and the basic geologic pro-

cesses that we have presented in this chapter result in a

rock cycle, in which rock moves from one physi cal state or

location to another (ˆ}ÕÀiÊ£Ó°{). The rock cycle is similar

to the other cycles of matter, such as the carbon and hydro-

logic cycles (see Chapter 5). However, rocks are formed

and move through the environment over geologic time,

much more slowly than the elements of the other cycles.

1. What are tectonic plates and plate boundaries?
   Where do earthquakes and volcanoes usually
   occur? Why?


2. What are the three types of rock? How are the
   three types of rock interconnected in the rock
   cycle?

minerals Elements

or compounds of

elements that occur

naturally in Earth’s

crust.