6.10B The student is expected to classify rocks as...
Transcript of 6.10B The student is expected to classify rocks as...
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.