6.10B The student is expected to classify rocks as metamorphic, igneous, or sedimentary by the processes of their formation.

First what is a cycle? Let’s do some brainstorming!

Now, what is the rock cycle? The rock cycle is: a series of processes on

and beneath the earth’s surface that slowly change rocks from one kind to another.

A rock is a naturally occurring solid mixture of one or more minerals, or organic matter

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

Rocks change over time through the rock cycle

Rocks may go through all or only

some stages of the rock cycle

Igneous Sedimentary Metamorphic

The differences among them have to do with how they are formed

Weathering - wearing away of Earth’s surface (minerals and rock break down into smaller pieces called sediment)

Erosion - moving of fragments of rock and soil (sediment moved)

Deposition - sediment is dropped in a new location (settles out of the water or wind that is carrying it in a new location)

Compaction - layers of sediment settle one on top of another and get squeezed together

Cementation - water seeps through layers of sediment and leaves behind minerals (sticking together of sediments)

Sediment - small pieces of rock, such as sand

Sedimentation – forming of sediment by deposition

Melting - change from a solid to a liquid state

Magma - molten mixture of

rock-forming substances, gases, and water in Earth’s mantle

Lava – magma that is ABOVE ground!

Sedimentary Rocks

Metamorphic Rocks Igneous Rocks

But how are they formed?

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

Sedimentary rocks are formed in multiple steps: Step 1 – weathering of existing rocks Step 2 - Sediments are moved from one place to another (erosion) Step 3- Sediments are deposited in

layers, with the older ones on the bottom Step 4 – final layers are formed from

cementing and compacting pieces of other rock together

Sedimentary Rocks are formed at or near the Earth’s surface

Form from cementing and compacting pieces of other rocks together No heat and pressure involved Strata – layers of rock Stratification – the process in

which sedimentary rocks are arranged in layers

These rocks are fairly soft and may break apart or crumble easily.

You can see sand, pebbles or stones in the rock, and it is usually the only type that contains fossils.

An example of cementation where minerals crystallize out of solution to become rock, this type also has fossils.

Limestone is a sedimentary rock composed primarily of calcium carbonate (CaCO3) in the form of the mineral calcite. It most commonly forms in clear, warm, shallow marine waters.

An example of conglomerate. You can see the pieces of the other rocks!

Gypsum

Sandstone

Shale

Limestone

Conglomerate

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

Morph – means to change Metamorphic rock is a rock that started as another rock and changed over time.

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

Metamorphic rock is a rock that heat and pressure cause metamorphose (change), but always remains a solid. metamorphic rock is formed when heat and pressure change the structure and physical properties of those rocks.

Two ways a metamorphic rock can form: It can be heated by nearby magma (#1) Increased temperature changes the composition of

the rock, minerals are changed into new minerals

Hornfels rock

The second way a metamorphic rock can form: pressure builds up in rocks that is deep within the Earth

Second line: Large pieces of the Earth’s

crust collide and the rock is deformed and chemically changed by heat and pressure

http://www.windows.ucar.edu/tour/link=/earth/geology/meta_regional.html&edu=high&fr=t

Ribbon-like layers and may have shiny crystals formed by minerals growing slowly over time on their surface.

These different ways that the rocks are formed cause different types of rocks.

Gneiss is foliated metamorphic rock that has a banded appearance and is made up of granular mineral grains.

Still a metamorphic rock, but mineral grains are not arranged in plains or bands

Marble is a non-foliated metamorphic rock that is produced from the metamorphism of limestone.

Formed from cooling magma from volcanoes Magma is a mixture of many minerals Magma cools and makes crystals. When lava cools quickly, no crystals form and

the rock looks shiny and glasslike. Sometimes gas bubbles are trapped in the rock

during the cooling process, leaving tiny holes and spaces in the rocks.

Intrusive Igneous Rocks: magma pushes into surrounding rock below the Earth’s surface

Extrusive Rocks: forms when magma erupts onto the Earth’s surface (lava), cools quickly with very small or no crystals formed

http://www.windows.ucar.edu/tour/link=/earth/geology/ig_intrusive.html&edu=high&fr=t

Granite is a light-colored igneous rock with grains large enough to be visible with the unaided eye. It forms from the slow crystallization of magma below Earth’s surface. The Texas capital is made from Texas pink granite.

Obsidian is a dark-colored volcanic glass that forms from the very rapid cooling of molten rock material. It cools so rapidly that crystals do not form.

This is an

example of

“glasslike” rocks.

The rock cycle is a series of processes on Earth’s surface and inside the planet that slowly change rocks from one kind to another.