The Earth’s surface is

constantly changing.

Mt. Saint Helen before and after eruption in 1980

Weathering- the breaking down

of rocks.

Types of Weathering

Physical or Mechanical

Weathering – the

breakdown of rock into

smaller pieces by

physical means

Chemical Weathering –

the breakdown of rock

into smaller pieces as a

result of chemical

reactions

Types of Physical Weathering

Plants

Roots grow into rocks, causing them to crack!

Types of Physical Weathering

Wind

As the wind blows it picks up small particles of sand and blasts large rocks with the abrasive particles, cutting and shaping the rock, like sand paper!

Types of Physical Weathering

Freezing Water Water freezes in existing cracks in a rock. When the water freezes, it expands, causing the cracks to get larger. This repeating process can split rocks in half!

Types of Physical Weathering

Freezing Water

Types of Physical Weathering

Moving Water Rocks break up when running water knocks them against each other.

Types of Physical Weathering

Moving Water

Moving water is the most powerful of all of the types of weathering. Over time, water cuts through rock like a knife.

Types of Physical Weathering

Glaciers

A glacier is a large river of ice that flows very slowly downhill.

Types of Physical Weathering

Glaciers

Stuck in the bottom of the glacier are sediments of various sizes that wear away the rock under the glacier as it moves downhill.

Types of Physical Weathering

Abrasion

The grinding and

wearing down of

rock and sand

particles by

friction due to

water, wind or

ice.

wind abrasion

water abrasion

Types of Chemical Weathering

Carbon Dioxide (CO2 )

Carbon Dioxide dissolved in water forms an acid that eats holes in the rock.

Types of Chemical Weathering

Oxidation

The reaction with oxygen. Oxidation is the process that causes rust. So just like your chain can turn to rust through oxidation, rocks can get rusty if they contain iron.

Erosion- when broken down rock

is moved by some force of

nature

Types of Erosion

Water

Rivers, streams, and runoff carry weathered rock or soil to another place

Types of Erosion

Water

Slow water carries rocks and soil downstream.

Types of Erosion

Water

Canyons are formed over time from the rivers slowly breaking away at rock and carrying them away.

Types of Erosion

Water

Water with more energy can cause greater erosion in a shorter period of time.

Types of Erosion

Ice

Glaciers moving over rocks breaks them down into smaller pieces and carries them away.

Weathering breaks down rock,

erosion moves the pieces of rock.

At some point the pieces or rock

will stop moving. This is called

deposition.

Deposition- when rock

sediments are laid down in a new

location

Types of Deposition

Water

Types of Deposition

Ice

At some point the glacier will stop

moving.

Types of Deposition

Wind Sand dunes are the result of deposition. When the wind stops moving, the sand stops moving. Sand dunes move frequently.

The process of weathering and

erosion are not easy to separate

because they happen

simultaneously.

The Rock Cycle

Forces deep inside Earth and at the

surface produce a slow cycle that

builds, destroys, and changes the

rocks in the crust.

Rocks change

from:

• weathering

Rocks change

from:

• weathering

• erosion

Rocks change

from:

• weathering

• erosion

• compression

Rocks change

from:

• weathering

• erosion

• compression

• compaction

• cementation

Rocks change

from:

• weathering

• erosion

• compression

• compaction

• cementation

• melting

Rocks change

from:

• weathering

• erosion

• compression

• compaction

• cementation

• melting

• heat / pressure

The series of changes that

rocks go through is called the

Rock Cycle.

Rock: A naturally occurring, solid mixture of minerals & organic matter.

Let’s break this down...

Rocks A rock is a naturally occurring, solid mixture of minerals &

organic matter.

Rocks are naturally

occurring

● They are not made by

humans

Rocks A rock is a naturally occurring, solid mixture of minerals &

organic matter.

Rocks are solid

Rocks A rock is a naturally occurring, solid mixture of minerals &

organic matter.

Rocks contain 2 or more

minerals

A rock is a naturally occurring, solid mixture of minerals &

organic matter.

Rocks contain organic

matter

• organic matter forms from

once-living organisms

A rock is a naturally occurring, solid mixture of minerals &

organic matter.

Organic - living or alive at

one time

Rocks are classified by how they are formed, their texture and their composition.

Texture refers to the size, shape, and

positions of the grains that make up

a rock.

Composition refers to the chemical

makeup of a rock.

granite composition

Plate movement starts the rock

cycle by forming magma.

subduction zones divergent

boundaries

When magma cools, it becomes

IGNEOUS ROCK.

Igneous rock

is often

found near

volcanoes

and mid-

ocean

ridges.

Igneous Rocks

Igneous Rocks The formation of igneous rocks depends solely on magma.

As you can see from this diagram, an oceanic plate drives itself

underneath the continental plate. The oceanic plate is more

dense than the continental plate, making it go underneath the

less dense continental plate. The oceanic plate activates the

zone of magma generation, causing it to come up through the

Earth’s crust and create a volcano. The magma that reaches

the surface is called lava, and when it cools, it forms igneous

rock.

As you can see from this picture, not all of the

magma reaches the surface. Some of it

remains in dikes, sills, and laccoliths. This

magma then cools over a long period of time

and becomes igneous rock also.

Igneous Rocks

The longer it takes for the magma or lava to cool, the

more time mineral crystals have to grow. The more

time the crystals have to grow, the larger the crystals

are and the coarser the texture of the resulting

igneous rock is.

Igneous Rocks

The less time magma takes to cool, the

less time crystals have to grow.

Therefore, the rock that is formed will be

fine grained. These contain very little

crystals, or if the cooling is very rapid, it

contains no crystals.

Igneous Rocks

Magma that cools beneath the surface

results in intrusive igneous rock

Intrusive igneous rocks are also referred to as plutonic

igneous rock. (Pluto was the god of the underworld in

Roman mythology).

Igneous Rocks

Intrusive igneous rocks have a coarse

texture. It forms as magma cools very

slowly under the surface. This slow

cooling allows large

crystals to form.

This photo shows granite, an intrusive igneous rock. Notice that

the rock contains visible minerals, reflecting the slow cooling

history of its parent magma.

Igneous Rocks

Magma that reaches the earth's surface is referred to as lava

The cooling of lava above the surface

results in extrusive igneous rock.

Sea –floor spreading is the process responsible for creating the

largest volume of extrusive igneous rocks.

Igneous Rocks

Extrusive igneous rock

cools quickly at the

surface. It contains very

small crystals or no

crystals.

Igneous Rocks

Igneous Rocks

Weathering. . .

• Breaks up the igneous rocks

The tiny pieces of broken rock are called sediments

or fragments.

Erosion. . .

• Carries the sediments away

Deposition. . .

•Eventually the sediments stop moving

• Overtime the layers of sediment compact together,

turning into rock

Sedimentary rock

is made from other

rocks that have

been weathered.

Forms when

sand and

sediments are

pressed tightly

and cemented

together.

Sedimentary Rocks

Sedimentary Rocks

Sedimentary rocks are often formed in layers.

This occurs because the rocks are often formed

underwater. A river or stream picks up sediment

along its path. When the river or

stream drains into

a large body of

water, the sediment

falls to the floor and

accumulates.

Sedimentary Rocks

Different kinds of sediment are carried

downstream at different times. This causes layers

of different colored particles to accumulate.

Sedimentary Rocks

Strata: layers of rock

Sedimentary Rocks

Stratification: the process by

which sedimentary rocks are

arranged in layers.

Sedimentary Rocks

This is a close-up view of

sandstone, a type of

sedimentary rock.

Notice the different colored

particles that this rock is

made up of.

This gives the impression that

it is made up of many different

kinds of rock that have been

broken down into small

pieces and have been

compacted tightly together.

Sedimentary Rocks

Sedimentary rocks form at or near Earth’s

surface.

Most of the rocks found on Earth’s surface

are sedimentary.

Sedimentary Rocks

Four different types of sedimentary rock are fossiliferous,

coal,

shale, and sandstone.

This is an example of a fossiliferous rock.

This simply means that fossils are present

in this sedimentary rock.

Coal is made of buried leaves, plants,

and other organic material. Where

coal is found makes scientists believe

that there was plant growth in the past.

This sedimentary rock is called shale. It

is formed by mud, which gives us the impression

that it was part of a river or lake bottom in

the past.

Sandstone is formed by sand that

could have been weathered by the

wind or could have accumulated in

part of a river bottom.

How fossils form:

1. Layers of sediments build up where

they are deposited into a body of water.

2. Dead animals sink to the bottom and

can become buried within the layers.

3. The layers form sedimentary rock, and

the dead animal remains, form fossils.

4. Fossils are exposed when the rock

that contains them is weathered and

eroded.

Fossils are most often found

in Sedimentary Rock.

Sedimentary Rocks

Scientists study these fossils to

learn how the earth has changed.

Sedimentary Rocks

What could these fossils tell?

• Shells at the top of a mountain. . .

- The area was once lower and under water.

• Fossilized trees on the bottom of a lake...

- The area was once dry.

• Warm-weather plant fossils in a frozen area.

. . - The area was once warmer.

Sedimentary Rocks

Rocks which form when igneous,

sedimentary or even

metamorphic rock is changed by

extreme heat or pressure.

Metamorphic Rocks:

are

“morphed,”

or changed

to a different

kind of rock.

Metamorphic Rocks:

Metamorphic Rocks

http://www.fi.edu/fellows/payton/rocks/create/metamorph.htm

usually form

deep in the

Earth.

Metamorphic Rocks:

This heat and

pressure can be

caused by

processes such as

folding, faulting and

subduction.

Metamorphic Rocks

Metamorphic rocks are rocks that were once of

one kind but because of heat, pressure, or a

chemical change, they were changed into

something else. These rocks are called

metamorphic rocks because they are “morphed,”

or changed to a different kind of rock. The rocks

could have been either igneous, sedimentary, or

even another metamorphic rock to begin with.

This rock is called

granite.

It is an igneous rock.

Because of heat and

pressure, it can be

changed to a

metamorphic rock

called marble.

This is what

becomes of

granite when it is

“morphed.” This

is marble.

This is a close-

up of

a section of

marble

rock.

Metamorphic Rocks

Metamorphic Rocks

A common way for

metamorphic rocks to form is

by the help of the formation of

igneous rocks. When igneous

rock is hot magma, the rock

surrounding this magma heats

up also. This rock will

become very hot and will

change because of the heat

and pressure.

When it cools, it will no longer

be exactly like what it was

originally. It will have changed

to metamorphic rock.

Metamorphic Rocks

Completing the cycle. .

. Extreme heat

and/or pressure

inside the Earth can

make metamorphic

rock melt.

Completing the cycle. .

. This melted

rock can be

pushed into

the mantle and

becomes

magma.

Completing the cycle. .

. This melted rock

eventually makes

its way back to

the surface.

Completing the cycle. .

. When it cools, it

forms igneous

rock.

Rock Cycle

Rock Cycle