CHANGING EARTH Rocks, fossils, earthquakes, volcanoes.

CHANGING EARTH

Rocks, fossils, earthquakes, volcanoes

Rocks and Minerals

Most rocks are composed of minerals

Descriptive terms about minerals found in rocks Shape Color Luster Texture Hardness

Igneous Rocks

Froms from magma (below ground) or lava (above ground)

Has crystals Classified by

Origin Texture Mineral Composition

Igneous Rocks

Origin Extrusive

Formed above ground Basalt

Intrusive Formed below ground Granite

Igneous Rocks

Texture Depends on size and shape of minerals (if

present) Rapidly cooling lava forms fine-grained

rocks with small crystals Slowly cooling magma forms course-

grained rocks with large crystals Does intrusive or extrusive rock have

larger crystals? Intrusive, it takes longer to cool so there is

more time for the crystals to grow

Igneous Rocks

Mineral composition Silica is found in magma and the

quantity varies. Low-silica magma forms rocks that are

dark in color. High-silica magma forms rocks that are

light in color. Different minerals determine colors in

the rock

Sedimentary Rocks

Sediment is small, solid pieces of material that come from rocks or living things.

Formed from other rock and exposed to forces that wear away Earth’s surface. Erosion – breaking up of rocks due to wind, running

water, ice (glaciers) Deposition – particles broken down by erosion are

deposited as loosely packed sediment Compaction – process that presses sediments together Cementation – while compaction is taking place,

minerals slowly dissolve in the water. The dissolved minerals crystallize & glue particles of sediment together.

Types of Sedimentary Rock

Clastic Rock fragments are squeezed together.

Fragments may be microscopic or large Shale, sandstone

Organic Forms from the thick layered remains of plant

and/or animals Coal, limestone

ChemicalCrystallized minerals that dissolve in a solution

Rock salt

Metamorphic Rocks

Heat and pressure deep beneath the Earth’s surface can change any rock into a metamorphic rock

High temperatures change the size and shape of the grains and crystals

Classified according to the arrangement of the grains that make up the rock

Types of Metamorphic Rocks

Foliated Grains arranged in parallel layers or bands,

may split into layers Slate

Nonfoliated Mineral grains arranged randomly, does not

split into layers Marble

Bookwork

Mass movement of landforms Gravity plays a role Water plays a role

Water erosion by rivers, ect How does the speed of the water affect the

amount and size of particles moved? Movement of rocks

The further a boulder moves down steam, the smaller it gets. Why?

Bookwork

Glaciers Leave behind U-shaped valleys Move the most material over time Form when more snow falls and melts

Waves Ocean waves are created by wind on the

surface Water particles move up and down, but not

in any other direction Wear down beaches and rocks

Rock Cycle

What process leads to the formation of sediment? Erosion! How is weathering related? What is soil sediment? How is it formed? Weathering and erosion of rocks into

smaller and smaller pieces makes soil

Soil Formation

Soil is made of tiny pieces of eroded rock and HUMUS HUMUS is a mixture of organic material. It

comes from broken down plant and animal matter

Majority of HUMUS comes from earthworms

The higher the HUMUS content, the better the soil

Rock Cycle

Three main types of Rocks: Sedimentary, Metamorphic, Igneous

Energy used to form or change rocks: Heat & Pressure (melting, etc)

Processes used to change rocks: Erosion, weathering, deposition,

cementation, melting

Rock Cycle

Metamorphic

Igneous

Sedimentary

Igneous Igneou

s

Metamorphic

MetamorphicSedimentary

Sedimentary

Rock Cycle Diagram

Copy the diagram of the rock cycle from page F 71

Age of Rocks

How do scientists determine the age of rocks? This age is often referred to as “relative age,” why? For very old rocks, scientists typically use a process

called carbon dating to determine their relative age. This process is based on the assumption that carbon has degraded at a particular rate for the entire history of the Earth.

Are the oldest rocks always at the bottom of the layers?

How could older rocks end up on top of younger rocks?

Folding & Faulting

The Earth’s surface goes through folding and faulting which pushes and turns the rock layers .

At fault lines, there will be noticeable “movement” in the rock layers. Pg G119

Earth’s surface is constantly changing and this can include the rock layers, especially at fault lines

Rock Layers Practice

Fossils

An index fossil helps to date rocks. Must be widely distributed Must represent an organism that existed

briefly Tell the age of the rock based on when the

fossil occurred

Fossils

How are fossils formed? Die, sediments are deposited on top,

compact down, pressure eventually cements all and turns the bones into rock

Will everything that dies turn into a fossil? What type of rock are fossils found in?

Sedimentary, sometimes in metamorphic How do fossils show evidence of the

changing surface of the Earth? Moving sediments, changing species, and?

Fossils, con’t

Why are more recently deposited rock layers more likely to contain fossils resembling existing species than older rock layers? Older fossils tend to represent species that

are extinct If an old fossil looks like a modern

organism, what can you conclude? The evolutionary rate of the organism is

slow.