48 terms

Science Ch. 5

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What characteristics are used to identify rocks?
the geologists observe the rock's COLOR, TEXTURE AND ITS MINERAL COMPOSITION.
How do we call the dark rock from the moon?
basalt
What is the Earth's crust made of?
rock
What are rocks made of?
They are made of mixtures of minerals and other materials, although some rocks may contain only a single mineral
What is granite made of?
It is made of minerals quartz, feldspar, mica, and hornblende, and sometimes other minerals.
What is a rock's texture?
It is the look and feel of the rock's surface. Some rocks are smooth and glassy. Others are rough or chalky.
What are grains?
There are the particles of minerals or other rocks. The grains give the rock its texture.
What are the three groups into which geologists classify rocks?
Igneous rock, sedimentary rock and metamorphic rock.
What is an igneous rock?
It forms from the cooling of molten rock, either magma below the surface or lava at the surface.
What is a sedimentary rock?
It forms when particles of other rocks or the remains of plants and animals are pressed and cemented together. Sedimentary rock forms in layers below the surface.
What is a metamorphic rock?
It is formed when an existing rock is changed by heat, pressure, or chemical reactions. Most metamorphic rock forms deep underground.
What methods do geologists use to determine the mineral composition of a rock?
They look at a small sliver of a rock under a microscope. But first they cut the rock very thin, so that light can shine through its crystals.
They also use testing the rock's surface with acid to see the carbonates.
They also test it with magnet to detect the elements of iron or nickel.
What do the three major groups of rocks have in common?
They all form under the surface.
How are the three major group of rocks different?
The way they are formed.
What characteristics are used to classify igneous rocks?
Their ORIGIN, TEXTURE AND MINERAL COMPOSITION
How are they classiffied according to their origin?
They are classified in EXTRUSIVE AND INTRUSIVE ROCKS
What is an extrusive rock?
It is an igneous rock formed from lava that erupted onto Earth's surface. BASALT is the most common.
What is an intrusive rock?
It is an igneous rock that formed when magma hardened beneath Earth's surface
What is the difference between extrusive and intrusive rocks?
Extrusive rocks form from lava that erupted onto the surface and intrusive rocks form from magma beneath the surface.
Give an example of an extrusive rock?
Basalt
Give an example of an intrusive rock?
Granite
Explain what causes an igneous rock to have a fine-grained or a coarse-grained texture?
Rapid cooling lava forms fine-grained igneous rocks with small crystals.
Slow cooling magma forms coarse-grained rock with large crystals.
Why are some igneous rocks dark and others light?
Because it depends on the silica content in the lava or magma. Lava that is low in silica usually forms dark-colored rocks such as basalt.
Magma that is high in silica usually forms light-colored rocks, such as granite.
What does the texture of an igneous rock depend on?
It depends on the size and shape of its mineral crystals.
What are the four types of textures in an igneous rock?
fine-grained
coarse-grained
glassy
porphyritic
What is s porphyritic texture?
It is when a rock with large crystals scattered on a background of much smaller crystals.
How are basalt and granite different in their origin, texture and mineral composition?
*BASALT:
ORIGIN, Extrusive
TEXTURE, fine-grained. Small crystals.
MINERAL COMPOSITION, dark-colored, low in silica.
*GRANITE:
ORIGIN, Intrusive
TEXTURE, coarse-grained. Large crystals.
MINERAL COMPOSITION, light-colored. Magma high in silica.
How do sedimentary rocks form?
They form from particles deposited by water and wind. If you have ever walked along a stream or beach you may have noticed tiny sand grains, mud, and pebbles.
What is sediment?
It is a small, solid pieces of material that come from rocks or living things.
Once sediment has been deposited, what processes change into sedimentary rock?
the processes of compaction and cementation change the sediment into sedimentary rock.
What are the three major kinds of sedimentary rocks?
clastic rocks
organic rocks
chemical rocks
Describe two ways in which limestone can form
1. Limestone can form when calcite that is dissolved in lakes, seas, or underground water comes out of solution and forms crystals.
2. Limestone can also form shen the calcite cements the shell particles together forming limestone.
What is a clastic rock?
It is a sedimentary rock that forms shen rock fragments are squeexed together.
What is an organic rock?
It forms where the remains of plants and animals are deposited in thick layers.
What is a chemical rock?
They form when minerals that are dissolved in a solution crystallize. For example Gypsum
Compare and contrast shale and sandstone. Include what they are made of and how they form?
Shale forms from tiny particles of clay. Sandstone from the sand on beaches, on the ocean floor, in riverbeds, and in sand dunes. Shale doesn't have many holes so water cannot pass thorugh them. Sandstone can easily absorb water through these holes.
How do coral reefs form?
When coral animals die, their skeletons remain, and more corals build on top of them.
How does coral become limestone?
Over time, coral buried by sediments can turn into limestone. Their limestone fossils are among the most common fossils on Earth. Limestone that began as coral can be found on continents in places where uplifth has raised ancient sea floors above sea level.
Why are living coral animals only found in water that is less than 40 meters deep?
...
What is an atoll?
It is a ring-shaped coral island found far from land. It develops when coral grows on top of a volcanic island that has sunk beneath the oceans surface.
Desscribe the process by which metamorphic rocks form?
Collisions between Earth's plates can push the rock down toward the hear of the mantle. Pockets of magma rising through the crust also provide heat that can produce metamorphic rocks.
What characteristics are used to classify metamorphic rocks?
The arrangement of the grains that make up the rocks.
Under what conditions do metamorphic rocks form?
heat and pressure deep benath Earth's surface.
How do geologists classify metamorphic rocks?
foliated.- They have their grains arranged in parallel layers or bands. Ex. Slate
nonfoliated.- The minerals grains in these rocks are arranged randomly. Ex. Marble
Which properties of a rock may change as the rock becomes metamorphic?
its appearence, texture, crystal structure and mineral content.
How does pressure change a rock?
The deeper rock is buried in the crust, the greater the pressure on that rock. Under pressure hundreds or thousands of times greater at Earth's surgace, the minerals in a tock can change into other minerals. The rock has become a metamorphic rock.
What is a metamorphic rock?
It is a rock that has changed its form.
What is the name of the most beautiful building build of marble?
The Taj Mahal in Agra, India.