Transcript Rocks - Lyme Central School District

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Rocks
http://geology.com/rocks/
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Why study rocks?
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Rocks are the pages in the history book of the earth. They tell
stories of times long past. From rocks, we have learned of
dinosaurs, trilobites and thousands of other life forms that
existed on earth once but are now no more.
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We have learned that the earth is constantly moving, shifting,
and changing. Rock is continually being created. It is heated,
squeezed, and weathered into new rocks. Finally, it is
remelted to start the process anew. By studying rocks, we
learn to read the pages of earth’s history.
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What is a rock?
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A rock is:
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A solid
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Naturally occurring
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Is made up of minerals or mineral like matter.
Rocks are classified by how they are formed. There are three
basic groups
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Igneous
• Igneous rocks form when molten lava (magma)
cools and turn to solid rock.
• Obsidian is nature’s glass. It forms when lava cools
quickly on the surface. It is glassy and smooth.
• Pumice is full of air pockets that were trapped when
the lava cooled when it frothed out onto the surface.
It is the only rock that floats.
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Sedimentary Rock
• Over time the layers of sand and mud at the bottom of
lakes & oceans turned into rocks. These are called
sedimentary rocks.
• Some examples of sedimentary rocks are sandstone
and shale.
• Sedimentary rocks often have fossils in them.
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Metamorphic Rock
• Metamorphic rocks are rocks that have changed
due to heat and/or pressure.
• Metamorphic rocks were originally igneous or
sedimentary, but due to movement of the earth's
crust, were changed.
• Marble and slate are examples of a sedimentary
rock that has been changed into a metamorphic
rock.
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Rock is continually being created. It is
heated, squeezed, and weathered into
new rocks. Finally, it is remelted to start
the process anew
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Slate
metamorphic
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Slate is a metamorphic rock that forms from mudstone or
shale.
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The color of slate is largely determined by the amount of iron
it contains, but it is normally a shade of gray.
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Slate can easily be broken into neat, thin sheets because of
its foliation.
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Used to be used as a chalkboard in schools.
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Shale
sedimentary
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Shale rocks are a type of sedimentary rock.
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They are usually found in areas where gentle waters have
deposited sediments that become compacted together.
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Shale usually forms in sheets.
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It is usually a gray color.
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Marble
metamorphic
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Marble is a metamorphic rock that forms when limestone is
subjected to heat and pressure.
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It is composed primarily of calcium carbonate.
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Our marble is a light color. You can see the crystals inside
make it sparkle.
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Limestone
sedimentary
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Limestone rocks are sedimentary rocks that are made from
the mineral calcite which came from the beds of evaporated
seas and lakes and from sea animal shells.
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This rock is used in concrete and is an excellent building
stone for humid regions.
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Our limestone is a light gray color.
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You can see little crystals inside.
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Limestone (Fossils)
sedimentary
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Limestone rocks are sedimentary rocks that are made from
the mineral calcite.
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This came from the beds of evaporated seas and lakes and
from sea animal shells.
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This limestone looks like the conglomerate because it has
little pieces of fossils inside.
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Obsidian
igneous
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Obsidian rocks are igneous rocks that form when lava cools
quickly above ground.
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Obsidian is actually glass and not a mixture of minerals. The
edges of this rock are very sharp.
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It is a shiny black rock.
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Conglomerate
sedimentary
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Conglomerate rocks are sedimentary rocks.
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They are made up of large sediments like sand and pebbles.
The sediment is so large that pressure alone cannot hold the
rock together.
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It is cemented together with dissolved minerals.
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Granite
igneous
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Granite rocks are igneous rocks which were formed by
slowly cooling pockets of magma that were trapped beneath
the earth's surface.
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You can see large crystals that shine in the rock.
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Granite is used for long lasting monuments and for trim and
decoration on buildings.
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Granite comes in different colors depending on the mineral
content. This granite is pink.
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Pumice
igneous
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Pumice rocks are igneous rocks which were formed when
lava cooled quickly above ground.
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You can see where little pockets of air had been. This rock is
so light, that many pumice rocks will actually float in water.
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Pumice is actually a kind of glass and not a mixture of
minerals.
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It is often light in color.
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Basalt
igneous
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Basalt is a dark-colored, fine-grained, igneous rock
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As it turns out, most of the ocean floor is basalt, and most of
the continents are granite.
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This is also abundant on the moon.
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Among other characteristics rocks are generally dark in
color and often have holes where pockets of air have been.
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Coal
sedimentary
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Coal is an organic sedimentary rock that forms from the
accumulation and preservation of plant materials, usually in a
swamp environment.
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Light, shiny black rock
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Used for energy. It is a fossil fuel.
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Quartz
(Mineral)
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Quartz is a very common mineral.
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Quartz is the most common mineral found in rocks.
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Looks like clear glass or a crystal
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Quartz is very important in industry for making gauges,
oscillators, resonators and watches.