Understanding Earth Processes & the Formation of ROCKS!

Understanding Earth Processes & the

Formation of ROCKS!

Molten = melted rock

Circulating heat currents

Hot, liquid rock circulating in currents within Earth cause continental and oceanic plates to move

Ocean floors and continents move like huge puzzle

pieces…

This super-continent was called Pangea

Continental plates were once very close together

1/3 land & 2/3 ocean

Earth is made up of…

When one plate slides under another, volcanoes form

Heat and pressure from the plate sliding under another cause molten rock to make its way out of the earth’s surface…

LAVA and volcanic eruption!

One plate sliding under another

Two plates colliding together, causing the land to buckle, would give us what?

Mountains!

Mountains erode (break down) continuously…

Gravity takes eroded rock pieces (sediment) downward towards water…

Sediment

makes it’s way

to the sea…

Erosion occurs from the wind as well…

…and also

by water

Plate movement,

Erosion, and all

Earth Processes give us…

Rocks!

Diversity of ROCKS!

Combinations of temperature, pressure, and chemical interactions within earth and on its

surface gives us a huge diversity of rocks!

Natural forces at work!

Rocks!• Made up of a mineral or a mixture of

minerals

• May also contain sediments and fossil remains of plants and animals

• They are the result of natural forces at work on our planet

• The study of rocks is called petrology

The elements oxygen, silicon, aluminum, iron, magnesium, calcium, potassium, and sodium make up 99 percent of all minerals on Earth.

The largest topaz crystal was found in Brazil in 1940. It weighs 596 pounds. It is on display in the American Museum of Natural History in New York.

Rock made up of sediment and fossils!

Rock made up of one type of mineral

Quartzite – made up of the mineral quartz

The most common mineral on earth is

quartz.

ROCKS are the records to our planet’s past!

• They indicate where rivers have flowed

• Where huge inland seas were located

• What organisms lived in those seas

• Where glaciers covered land

Dry river beds…only sediment and rocks remain!

Rocks indicate where water levels once were…

Basic Rock Types

• All rocks fall into one of 3 basic groups:

1. Igneous

2. Sedimentary

3. Metamorphic

Igneous RocksForm from the coolingof liquid rock(magma) that came up from deep within theearth. It is the melting and solidification of metamorphic rocks!Igneous rock is the most common material of the earth’s crust!

Igneous means “fire”

Igneous Rocks:• Often hidden by sedimentary rock• Can be intrusive or extrusive igneous rock• If recrystallization and solidification occurred

below the earth’s surface (such as the formation of granite), than the rock is intrusive

• If the rock formed on the earth’s surface from cooling of volcanic lava (such as obsidian and basalt), than the rock is extrusive

Igneous Rocks:• If rock formed from a slow cooling, the rock will

contain coarse-textured minerals (Example = granite)

• If rock formed from a fast cooling, the rock will contain fine-textured minerals (Example = basalt)

• If rock contains a high amount of silica, it will be light in color and weight, and be known as acidic

• If rock contains high amounts of iron and magnesium, it will be dark-colored and heavy, and be known as basic

Basalt

Most common extrusive and basic igneous rock

Granite

Most abundant of all igneous rocks

Gabbro

Rhyolite

Scoria

Obsidian

Looks like shiny black glass as a result of very fast cooling of volcanic lava

Pumice

Porous (has many holes) and floats on water!

Sedimentary Rocks• Form from the burial and cementing of

layers of sediment broken off of other rock types and deposited in water. Weathering and erosion can be caused by wind, waves, gravity, or water. Rivers carry sediment for long distances.

Rock formation from years of wind erosion…

Sediment that was swept away eventually became sedimentary rocks!

Sediment:

• Sand

• Gravel

• Mud

• Clay

Name of Particle 

Size Range  Loose Sediment

Consolidated Rock 

Boulder  >256 mm  Gravel 

Conglomerate or Breccia (depends on rounding) 

Cobble  64 – 256 mm  Gravel 

Pebble  2 - 64 mm  Gravel 

Sand  1/16 –2 mm  Sand  Sandstone 

Silt  1/256 - 1/16 mm 

Silt  Siltstone 

Clay  <1/256 mm  Clay  Claystone, mudstone, and shale

Compaction from the weight of accumulating sediment results in layers that become hardened and turn to sedimentary rocks!

•Most sedimentary rocks form under water.

•Most of the earth has been covered by water some time in the past. 70% of the earth is covered by water now. So sedimentary rocks are common all over the world.

•Sedimentary rocks are often rich in fossils.

•Many sedimentary rocks may have cross-bedding, mud cracks, worm burrows, raindrop impressions.

•70% of rocks found on Earth are sedimentary.

Two Types of Sedimentary Rocks!

• Rocks formed from sediment (sand, silt, clay, or mud) or clasts (pieces) of rock are known as clastic sedimentary rocks

• Rocks formed from processes known as chemical precipitation or organic activity are known as non-clastic sedimentary rocks

Shale

Nonclastic (clay)

Conglomerate

Clastic

(rounded pebbles)

Sandstone

Clastic (sand)

Limestone

Non-Clastic (calcium carbonate precipitate)

Bituminous Coal

Non-Clastic

(buried peat moss material)

Peat that gets buried over time and compressed deep into the earth eventually gives us bituminous coal. Bituminous coal is carbon-rich and is an excellent source of energy. Humans burn coal to release that energy in the form of heat.

Gypsum

Non-Clastic sedimentary rock that can be scratched with your fingernail!

Metamorphic Rocks• Form from

pressure and extreme temperatures changing the chemistry of igneous and sedimentary rocks that got buried into the earth over time.

Metamorphosis

• Complete change of character, appearance, or condition.

• Involves heat, pressure, and chemical action

• Process can occur more than once• Results in the recrystallization of original

rock (sedimentary or igneous) and a different mineral composition

Limestone metamorphosed to marble!

Sandstone metamorphosed to quartzite!

Shale metamorphosed to slate!

Gabbro metamorphosed to schist!

Many metamorphic rocks contain flat minerals such as mica and needle-like minerals such as hornblende

MicaHornblende

Slate

These rocks can split into thin sheets!

Marble

Can be polished and made into kitchen countertops!

Schist

Gneiss

What a nice rock!

Gneiss

The oldest known rock lies in Canada. The Acasta gneiss, a metamorphic rock,

is 3.96 billion years old.

Rock Cycle is a sequence of processes or events

involving the formation, alteration, destruction, and reformation of rocks

Taj Mahul in India Built

between 1632 and 1654 is made entirely out of marble!

Up to 100,000 tons of rock a year fall to earth from space. The largest meteorite in the world lies in the ground in Africa

and weighs more than 60 tons.

A 2.2 lb rock collected from the moon during the Apollo 16 mission. This rock formed when older

moon rocks were fragmented and and then fused back together by a meteorite impact about 3.9

bya. The shiny black material on the side is impact-generated glass.

The Importance of Rocks and Minerals

Name Type of Rock Use

Basalt Igneous Used in road building

materials

Calcite Mineral Used in cements and mortars and the

production of lime

GraniteIgneous

Used for buildings, monuments, and tombstones

Marble Metamorphic Used in building, floors, tile in bathrooms

Obsidian Igneous Used in making arrowheads and knives

PumiceIgneous

Used in scouring, scrubbing, and polishing materials

Quartz Mineral Used in making glass, electrical components,

and optical lenses

Sanstone Sedimentary Used in the building industry for houses

Slate Metamorphic Used for roofs, chalkboards, and patio walks

Landforms• Part or area of the Earth’s surface that has a

distinctive shape or topography

Weathering

is a series of natural processes, both physical and chemical, that act to change exposed rock into mineral and rock particles and chemical compounds in solution.

Independent Variable

• is the one variable that is changed on purpose in an experiment.

Dependent Variable

• is the outcome that is being measured in an experiment.