An Introduction

What does a rock want to be when it grows up?

A ROCK STAR

We’ve already learned about

something called the

WATER CYCLE

so we know a cycle is a

process that

REPEATS

There are three types of rocks:

Lava

Magma Pool

Sediments

Igneous

Sedimentary

Metamorphic

The Rock Cycle . . .is a group of

changes

The ROCK CYCLE is NOT a circular cycle but rather a process by which one rock changes into another which can take billions of years.

What do you do to a baby rock?

ROCK IT!

• Most of the Earth’s crust is made up of rock

• Rocks are made up of one or more minerals and have been formed by heat or pressure in the earth

Did you know?

• Sedimentary rock is less than 5% of the Earth’s crust but it covers 75% of the Earth’s continental surface

• 95% of the Earth’s crust is igneous rock and metamorphic rock

Classification

Rocks are classified by:

1. How they were formed

2. Composition – what the rock is made up of

3. Textures – sizes, shapes, and positions of grains

M = Melting W/E = Weathering & Erosion C = Cooling H/P = Heat & Pressure C/C = Compacting & Cementing

The ROCK CYCLE

Magma

CM

W/E

H/P

W/E

W/E

H/P M

C/C

Metamorphic

Sedimentary

Sediments Igneous

What is a rock’s favorite cereal?

Cocoa Pebbles

Igneous Rock

Rock that forms from the cooling of magma or

lava

Magma

Origins – How rock melts

1. Temperature increases

2. Composition changes = lowers the melting point of the rock

3. Pressure on rock decreases (pressure released)

Composition & Textures

Glue or paste your Composition & Texture table in this section of your foldable

The amount of time it takes for magma or lava to cool determines the texture

Formation of Igneous Rocks

Pyroclasts

Extrusive

Intrusive

Porphyry: partially crystalline

Fig. 5.3

Granite rocks are igneous rocks which were formed by slowly cooling pockets of magma that were trapped beneath the earth's surface. Granite is used for long lasting monuments and for trim and decoration on buildings.

Scoria rocks are igneous rocks which were formed when lava cooled quickly above ground. You can see where little pockets of air had been. Scoria is actually a kind of glass and not a mixture of minerals.

Pumice rocks are igneous rocks which were formed when lava cooled quickly above ground. You can see where little pockets of air had been. This rock is so light, that many pumice rocks will actually float in water. Pumice is actually a kind of glass and not a mixture of minerals. Obsidian rocks are igneous rocks that form when lava cools quickly above ground. Obsidian is actually glass and not a mixture of minerals.

How Igneous Rock Is Formed

Igneous rocks are called fire rocks

and are formed either

underground or

above ground

Intrusive Igneous Rock

Underground – Inside

• Magma becomes trapped in small pockets

• Magma cools SLOWLY underground - bakes

•Usually coarse-grained

Split the section labeled ROCK FORMATION into two sections

Above ground - Outside

• Formed when volcanoes erupt

• Magma above the earth is called lava • Lava cools QUICKLY above ground and in water

• Usually fine-grained

Extrusive Igneous Rock

Magma is molten rock that is deep underground

Magma forms “intrusive” igneous rock

This is an image of the eruption of

Stromboli volcano

Lava

forms

“extrusive”

igneous rock

Basalt is an extrusive igneous rock that is very dark in color.

It is the most common type of rock in the Earth's crust and it makes up most of the ocean floor.

Sedimentary Rock

Rock that forms when sediments are

compacted and cemented together

Origins of Sedimentary Rock

•Erosion - bits of earth washed downstream and settles to the bottom of the rivers, lakes, and oceans.

•Eroded earth is deposited on top of each other.

•Layers are pressed down and turn into rock

Sandstone rocks are sedimentary rocks made from small grains of the minerals quartz and feldspar. They often form in layers as seen in this picture. They are often used as building stones.

Limestone rocks are sedimentary rocks that are made from the mineral calcite which came from the beds of evaporated seas and lakes and from sea animal shells. This rock is used in concrete and is an excellent building stone for humid regions.

Shale rock is a type of sedimentary rock formed from clay that is compacted together by pressure. They are used to make bricks and other material that is fired in a kiln.

Composition1. Clastic – rock & mineral

fragments stick together.

The size & shape influences their name

The rocks that make high ridges are much more

resistant to weathering than the surrounding

rocks.

Cathedral Rock in Arizona is made of a clastic rock called sandstone. . These rocks are more than 250 million years old and are now being weathered and eroded away by the creek.

This stream carries sediment that has weathered from mountains in Alaska

Sediment (A) may someday become a clastic rock (B) if compacted and cemented together.

Forms when minerals crystallize out of a solution like sea water and becomes rock

2. Chemical Sedimentary Rock -

Gypsum rocks are sedimentary rocks made up of sulfate mineral and formed as the result of evaporating sea water in massive prehistoric basins. It is very soft and is used to make Plaster of Paris, casts, molds, and wallboards.

Conglomerate rocks are sedimentary rocks. They are made up of large sediments like sand and pebbles. The sediment is so large that pressure alone cannot hold the rock together; it is also cemented together with dissolved minerals.

These pebbles were deposited in a stream that once flowed over this area in Indiana, USA thousands of years ago.

Ripples in beach sand , such as those in the upper photograph (A) may someday become a rock like the sandstone in the lower photograph (B).

This sandstone was part of a beach over 200 million years ago in the Triassic period.

3. Organic Sedimentary Rock -

Forms from the remains of organisms

Coquina

StructuresFeatures tell the story of formation

•Layers are called strata

•Strata differs depending on the kind, size and color of the sediment

•The rate of deposition can affect the thickness of layers

What could affect the rate of deposition (deposits)?

The amount of rain – more = flooding & less = drought

•Weathering (wind & water) affects the design of sedimentary rock

Weathering (wind & water) affects

the design

of

sedimentary rock

Metamorphic RockRock that forms when the texture and composition of pre-existing rock CHANGES due to heat or pressure

•The pre-existing rock is often referred

to as the

“Parent Rock”

Origins of Metamorphic Rock

1. Contact Metamorphism – Rock comes into “contact” with magma and cooks

2. Regional Metamorphism – Enormous pressure builds up in deeply buried rock

Rocks that have “MORPHED”

into another kind of rock

Schist rocks are metamorphic. These rocks can be formed from basalt, an igneous rock; shale, a sedimentary rock; or slate, a metamorphic rock. Through tremendous heat and pressure, these rocks were transformed into this new kind of rock.

Gneiss rocks are metamorphic. These rocks may have been granite, which is an igneous rock, but heat and pressure changed it. You can see how the mineral grains in the rock were flattened through tremendous heat and pressure and are arranged in alternating patterns.

The more you try to be

gneiss, the more you get

taken for granite!

Composition

Scientist understand the history of the rock

based on the minerals present and how they

have changed

TexturesMetamorphic rock is described by two types of textures: Foliated and Non-foliated

1. Foliated – minerals are aligned and look like pages in a book (A distinct pattern)

2. Non-Foliated – minerals don’t appear to be in any pattern

Start Apply increasing

heat

&

pressure

Finish

Here's a chart of some of the key characteristics

that can help you identify the rocks within these

three main classes.

Crystals: Small, flat surfaces that are shiny or sparkly, like tiny mirrors.Fossils: Imprints of leaves, shells, insects, or other items in the rock.Gas bubbles: "Holes," like Swiss cheese, in the rock.

Glassy surface:A shiny and smooth surface, like colored glass.Ribbon-like layers: Straight or wavy stripes of different colors in the rock.Sand or pebbles: Individual stones, pebbles, or

sand grains visible in the rock.

Review:There are how many types of rocks?

3

Rocks are put in one of these categories (classified) by three things. What are they?

1. Composition 2. Texture 3. How it formed

Igneous rock is classified by composition - being light or dark but we use what words?

Mafic or Felsic

Igneous rock is classified by texture – coarse-grained or fine-grained but we use words to describe where they formed. What words do we use?

Intrusive or Extrusive

1. Clastic 2. Chemical 3. Organic

Sedimentary rock is classified by composition – how it was formed in one of three ways. What are the three ways?

Metamorphic rock is classified by composition – What minerals are present and by texture – but we describe the texture based on the presence of a pattern or a lack of a pattern. What words do we use to describe the pattern or lack of a pattern?

Foliated or Non-foliated

From the cooling and solidification of lava or magma

Igneous rock forms how?

Sedimentary rock forms how?

From the erosion and weathering of rock

What type of rock can become sedimentary rock?

All types

Metamorphic rock forms how?

From intense heat & pressure changing pre-existing rock

M = Melting W/E = Weathering & Erosion C = Cooling H/P = Heat & Pressure C/C = Compacting & Cementing

The ROCK CYCLE

Magma

CM

W/E

H/P

W/E

W/E

H/P M

C/C

Metamorphic

Sedimentary

Sediments Igneous

The END!