RocksRocks

Rocks! What makes up

Earth’s Crust

Three types of rocks…Three types of rocks…

Igneous MetamorphicSedimentary

What is a rock?What is a rock?

A rock is a solid that forms in nature. It may have one or more types of minerals within it (or no minerals at all).

Some rocks have minerals, Some rocks have minerals, some don’t…some don’t…Minerals are clearly

visible in some igneous rocks like…..

There are no mineralcrystals in obsidian.

What is the rock cycle?What is the rock cycle?Natural

processesthat… Forms Changes Breaks down

rocks

Rock isreformedinto another type of rock.

The rock cycle in action…The rock cycle in action…

The rock cycleshows thethree types ofrocks.

IgneousMetamorphicSedimentary

Listen and watch how the processes formed the three types of rocks.

QuickTime™ and aCinepak decompressor

are needed to see this picture.

Forms when molten rock cools and becomes a solid.

Igneous rocks may form

inside Earth or on Earth’s surface.

Intrusive-forms when magma cools within the Earth.

Extrusive-forms when lava cools on the surface.

Igneous Rock

What is a rock’s texture?What is a rock’s texture?Texture refersto the size ofthe mineral crystals:coarse, fine, glassy

Pumice

Coarse

FineGlassy

Textures of Intrusive Igneous RockTextures of Intrusive Igneous Rock

The size of mineral crystals depends on how quickly the magma or lava cooled.

The high temperatures of the interior of the Earth causes magma to cool slowly.

Slow cooling allows large crystals to form.

Intrusive Rocks

How are we able to see intrusive How are we able to see intrusive rocks?rocks?

Ship Rock formed 30 million years ago.

Magma cooled to form intrusive rock.

Intrusive igneous rock has been left as weaker

rock (like sedimentary) has worn away

due to weathering & erosion.

Textures of Extrusive Igneous RockTextures of Extrusive Igneous Rock

The surface of Earth is much cooler than the interior, causing lava to cool quickly.

There is no time for large mineral crystals to form.

Composition of Igneous Rocks…Composition of Igneous Rocks…

Most igneous rocks are made up of silicate materialsThe color tells you how much silica the rock has.

High levels of silica will be lighter in color.

Low levels of silica will be darker in color.

What type of rock was carved to What type of rock was carved to create Mount Rushmore?create Mount Rushmore?

Igneous!

Interesting Rock FormationsInteresting Rock Formations

#1

#2

#3

#4

Which of these is a rock?

A. halite B. graniteC. mica D. quartz

Answer: B. granite

Which is formed from cooling magma?

A. metamorphic B. igneousC. sedimentary D. sandstone

Answer: B. igneous

Sedimentary Rocks: “something Sedimentary Rocks: “something that settles”that settles”

Small pieces of rock turn into pebbles, gravel, sand, clay, and plant & animal matter. They tumble down rivers and streams.

These pieces settle in a new place and begin to pile up and the sediments form flat layers.

Sediments harden into rock in Sediments harden into rock in two ways. two ways.

Compaction- layer after layer of sediments are deposited, they are pressed together tightly to form rock.

Cementation- sediments are held together by minerals that have crystallized between them (acting as cement).

Sedimentary rocks Sedimentary rocks may be rich in….may be rich in….

Fossils- Remains or trace of an organism from long ago.

Coal-Made up of the remains of dead plants. The coal we use today formed millions of years ago in swamps.

Limestone-made of carbonate minerals (calcite) from seashells that settle on the bottom of the ocean.

COAL: Natures rock…..COAL: Natures rock…..Coal is made from dead plants and over time pressed into the Earth.

Sedimentary Rock tells a story Sedimentary Rock tells a story about Earth’s past…about Earth’s past…

These rocks are laid down in layers with the oldest on the bottom.

Do you remember what rock layers are called?

Law of Superposition or stratification!

Do you remember?Do you remember?What layer of rock is the… Oldest?

Oldest

Youngest

Metamorphic Rock=Metamorphic Rock=Changed RockChanged Rock

Sedimentary Metamorphic

Composition and Texture: Composition and Texture: a way to identify metamorphic rocka way to identify metamorphic rock

When mineral grains line up in parallel layers, the metamorphic rock is said to have a Foliated texture.

Slate Gneiss

Non Foliated Metamorphic RockNon Foliated Metamorphic Rock

Typically made up of one type of mineral so different minerals can not line up in bands.

Marble formed from limestone

Quartzite forms from Sandstone

When a metamorphic rock does not have “foliation” it typically has only one mineral, therefore no parallel banding patterns.

Metamorphic Rocks are formed when…

+

Metamorphic Rock

=+

How much of Earth’s Crust is How much of Earth’s Crust is made of each type of rock?made of each type of rock?

Surface = 75% Sedimentary Rock Entire Crust = 95% Igneous and Metamorphic Rock

What type of rock is the most commonon the surface of Earth’s crust?

A. metamorphic B. sedimentaryC. igneous D. igneous and metamorphic

Answer: D igneous and metamorphic

95% of Earth’s entire crust consist of what type(s) of rock?

A. metamorphic B. igneousC. sedimentary D. sandstone

Answer: C. sedimentary