Chapter 4 Rocks

Why should I care?

You’ve just been abducted by aliens!!!

What do I use to chop down trees with to build my new fortress?

They’ve abandoned you on another planet. NOW WHAT?!?!?!

What kinds of rock will work? What can I do to make the axe? What else can I use rocks for?!?!?!

But first……..

It is a hard substance that is made of one or more minerals

Rocks are classified according to how they are formed.

1. Igneous Rocks –

“fire formed”

2. Sedimentary Rocks - “sediment rocks”

3. Metamorphic Rocks - “changed rock”

The natural process of one rock type changing into another rock type.

Magma

IgneousRock

SedimentSedimentary

Rock

MetamorphicRock

Heat, Pressure,& Chemical Reactions

Melting

Cooling & Crystallizing

Erosion & Weathering

Cementing & Compacting

Rocks that are formed from magma (below) or lava (above)

Make up a large portion of the crust.

Based on composition and texture.

the size, shape, & relationships of the mineral crystals in a rock

a. Coarse Grain - large crystals

Granite Diorite

b. Fine Grain - small crystals

c. Vesicular - full of holes because of gas bubbles

PumiceBasalt

RhyoliteBasalt

d. Glassy - cools too fast to form crystals

e. Pyroclastic – cemented volcanic ash, cinders, & bombs

Obsidian

Scoria

Pumice

Magma will cool and form mineral crystals at different temperatures.

Geologists can identify igneous rocks based on the specific minerals in the rock.

Ж Igneous rocks with Igneous rocks with finefine grain grain texture are made from lavatexture are made from lava(Extrusive). (Extrusive).

ж Igneous rocks withIgneous rocks with coarse coarse grain grain texture are made from magma texture are made from magma (Intrusive).(Intrusive).

Rocks formed by the cementing & compacting of small rock particles.

1. As rocks are broken down by water & wind (weathering/erosion,) the rock particles (sediment) will sink to the bottom of a water source.

2. Over a long period of time the sediment will build up in layers. The upper layers cause pressure on the lower layers (compacting.)

------physical process

Pressure =compacting

3. In other cases, chemicals within the sediment will “glue” the sediment together forming a rock (cementing.)

-----chemical process

Grouped based on how the rock was formed & where the sediment came from.

Sedimentary rocks that are made of previously existing rock fragments.

These rocks are named based on the size & shape of the rock fragments within the main rock.

EX: Sandstone & Shale

Conglomerate

Breccia

Sandstones

Shales

Includes rocks that were formed as a result of mineral crystallization when water evaporated.

Ex: rock salt

Includes organic rocks such as coal & fossils

Includes cavernous rocks such as stalactites & stalagmites.

Includes microcrystaline quartz rocks

EX: Limestone & Flint

Flint/Chert

Limestones

A rock that has changed in form because of heat, pressure, and/or chemical reactions.

When a rock goes through a change it is called metamorphism.

Metamorphism can affect igneous and/or sedimentary rocks that are deep within the crust.

Heat will cause the minerals within the rock to break down to form more heat resistant minerals.

Pressure will force the minerals to rearrange themselves.

Chemicals within the rocks can alter or change the chemical make-up of the rock.

Shale----------Slate

Granite----------Gneiss

Limestone--------Marble

Based on the arrangement of the grains within the rock.

Metamorphic rocks that have mineral crystals arranged in parallel layers or bands.

The rock tends to break along the bands.

EX: Schist, Gneiss, & Slate

Metamorphic rocks that are NOT banded and do NOT break into layers.

EX: Marble & Quartzite

Marble Quartzite

How are rocks my friend in this situation?

To Do list:

1.

Things I need to live:

1.