The rock cycle

The changes form a cycle, called "the rock cycle." The way rocks change depends on various processes that are always taking place on and under the earth's surface.. However, before the

How Rocks Change

All rocks change slowly from one type to another, again and again The changes form a cycle, called "the rock cycle."

The way rocks change depends on various processes that are

always taking place on and under the earth's surface Now let's take

a closer look at each of these processes

Heat & Pressure

 Heat

Deep below the earth's surface, temperatures are hot enough to melt most rocks However, before the melting point is reached, a rock can undergo many changes while in a solid state — changing from one type to another without melting.

An additional factor that can transform rocks is the pressure caused

by tons of other rocks pressing down on it from above.

Heat and pressure usually work together to alter the rocks under the earth's surface This kind of change is called metamorphism

which results in a metamorphic rock.

http://screencast.com/t/PCA0IxoNjtB

Melting & Cooling

Melting

The high temperatures required to melt a rock are generally found only deep within the earth It takes temperatures between 600 and 1,300 degrees Celsius (1,100 and 2,400 degrees Fahrenheit) to melt a rock, turning it into a substance called magma (molten rock)

Click here to see the melting and cooling video:

http://screencast.com/t/HE4w6byZdpU

Weathering & Compacting

The Rock Cycle

http://www.learner.org/interactives/rockcycle/types.html

Types of Rocks

Rocks are not all the same!

The three main types, or classes, of rock are sedimentary, metamorphic, and igneous and the

differences among them have to do with how they are formed.

Sedimentary

Formed from particles of sand, shells, pebbles, and other fragments of material.

These particles or sediments accumulate and harden into rock.

You can often see sand, pebbles, fossils or stones in the rock.

Examples of this rock type include conglomerate and limestone.

Metamorphic

Formed under the surface of the earth

Go through metamorphosis (change) that occurs due to intense heat and pressure (squeezing).

Usually have ribbon like layers and may have shiny crystals.

Examples of this rock type include gneiss and marble.

Igneous

Formed when magma or lava cools and hardens

When lava cools very quickly, no crystals form and the rock looks shiny and glasslike.

Sometimes gas bubbles are trapped in the rock during the cooling process,

leaving tiny holes and spaces in the rock.

Examples of this rock type include basalt and obsidian.

What to Look For:

 Here's a chart of some of the key characteristics that can help

you identify the rocks within these three main classes.

Sand or pebbles

Individual stones,

pebbles, or sand grains

visible in the rock.

Fossils Imprints of leaves, shells, insects, or other items in the rock.

Crystals Small, flat surfaces that are shiny or sparkly, like tiny mirrors

Sedimentary Igneous Metamorphic

http://www.learner.org/interactives/rockcycle/types.html



Let’s Review

To take the quiz hit the start button If you don’t feel ready to take the quiz and need to look over the

information more, press the back arrow.

 Which type of rock is this?

metamorphic

sedimentary

igneous

Click this button to try again:

You can tell that this rock is igneous because of

its shiny, glasslike surface.

 Which type of rock is this?

metamorphic

sedimentary

igneous

Click this button to try again:

You can tell that this rock is sedimentary because it has large chunks of other rocks in

it.

 Which type of rock is this?

metamorphic

sedimentary

igneous

Click this button to try again:

You can tell that this rock is metamorphic

because of the rippled layers.

 Which type of rock is this?

metamorphic

sedimentary

igneous

Click this button to try again:

You can tell that this rock is sedimentary because you

can see fossils embedded in the rock.

 

The End!

Hopefully you have learned a lot about the rock cycle!

Information and videos from: http://www.learner.org/interactives/rockcycle/types.html