METAMORPHIC ROCKS AND THE ROCK CYCLE

Chapter 9 Section 3Pgs 284-288SPI’s 0707.7.2 & 0707.7.3

LEARNING OBJECTIVES

In this section we will:

1. Describe the conditions needed for metamorphic rocks to form.

2. Explain how all rocks are linked by the rock cycle.

NEW VOCABULARY

Foliated Metamorphic rock Nonfoliated Rock cycle

NEW ROCK FROM OLD ROCK

Many conditions on Earth cause rocks to form and then to change

Low temperature processes (erosion and weathering)

High temperature conditions (molten rock, magma)

Pressures and temperatures increase as rocks are compressed or buried deeply Grain sizes and chemistry are changed

Rocks also change when continents collide

METAMORPHIC ROCK

New rocks are formed when existing rocks are heated or squeezed but not melted

“change of form” Rocks take on a whole new look after

being exposed to extreme temperatures and pressures

Figure 21 pg 285

TYPES OF CHANGED ROCK

New metamorphic rocks can form from any existing type of rock

Texture can be used to classify rocks Texture differences in metamorphic

rocks can be used to divide them into 2 main groups: Foliated Nonfoliated

FOLIATED ROCK

Foliated rocks: have visible layers or elongated grains of minerals

These rocks have been heated and squeezed into parallel layers

Many have bands of different-colored minerals

Examples include: Slate, gneiss, phyllite

NONFOLIATED ROCK

These rocks DO NOT have distinct layers or bands

Examples include quartzite, marble, soapstone

More even in color Mineral grains do not appear

to be arranged in any distinct pattern

Quartzite forms when quartz sand grains in sandstone re-crystallize after they are squeezed and heated

THE ROCK CYCLE

Model scientists use to describe how different kinds of rocks are related and how rocks change from one type to another

The cycle can take MILLIONS of years Figure 23, page 287

JOURNEY OF A ROCK If you pick any point on the cycle, you can see

how that rock could become any other rock The blob of lava that oozes to the surface

forms igneous rock Wind, rain, and ice wear away at it and it

breaks into small pieces (sediment) Sediment is carried by streams and rivers

where it piles up over time Weight above presses on sediment below Mineral-rich water “glues” or cements it

together If the rock is buried deeply, pressure and heat

inside Earth can change it to metamorphic rock

REVIEW QUESTIONS

What are two factors that can produce metamorphic rocks?

List some examples of foliated and non-foliated rock. Explain the differences in the two types of metamorphic rocks.

What is the difference between igneous and metamorphic rocks?

What does the rock cycle describe?