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 Igneous Rock Sediment Sedimentary Rock Metamorphic Rock 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 Rhyolite Basalt

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 fine grain texture are made from lava (Extrusive). ж Igneous rocks with coarse grain texture are made from magma (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.