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Chapter 5 - Rocks
Rocks
65
Science
7th Grade
11/28/2012

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Cards

Term
What do geologists observe when studying a rock sample?
Definition
    • The rock's mineral composition
    • The rock's color
    • The rock's texture
Term
What are rocks made of?
Definition
Rocks are made of mixtures of minerals and other materials.
Term
Some rock's contain a single _____________.
Definition
mineral
Term
Approximately how many minerals make up most of the rocks of Earth's crust & what are they known as?
Definition
20 & rock-forming minerals
Term
What can help provide clues to the rock's mineral composition?
Definition
Its color.
Term
If you test the surface of a rock with acid what will you determine?
Definition
You will determine whether the rock includes minerals made of compounds called carbonates.
Term
What are three things you can say about Basalt?
Definition
  1. It is a dark-colored rock.
  2. It has low silica content.
  3. Unlike granite, basalt has mineral crystals that are too small to be seen without a hand lens.
Term
What is granite made up o?
Definition
  • quartz
  • feldspar
  • hornblende
  • mica
  • (It may also contain other minerals)
Term
Most rocks are made up of particles of minerals or other rocks, which geologists call ______________.
Definition
grains
Term
To a geologist, a rock's _____________ is the look and feel of the rock's surface.
Definition
texture
Term

To describe a rock's texture, geologists use terms based on the:

  1.   
  2.   
  3.   
of the grains.
Definition
  1. size
  2. shape
  3. pattern
Term

What is the grain size of slate?

 

Definition
fine
Term
What is the grain size of diorite?
Definition
coarse
Term
What is the grain size of flint?
Definition
no visible grain
Term
When the grains in a rock are large and easy to see, these rocks are said to be ______________.
Definition
Coarse-grained
Term
When the grains are so small that they can only be seen with a microscope they are said to be ____________.
Definition
fine-grained
Term
Using what three criteria can geologists classify a rock according to its origin?
Definition
  1. color
  2. texture
  3. mineral composition
Term
What are the three major groups geologists can classify rocks?
Definition
  1. Igneous rock
  2. Sedimentary rock
  3. Metamorphic rock
Term
How does the igneous rock form?
Definition
from the cooling of magma or lava
Term
How do most sedimentary rocks form?
Definition
When the particles of other rocks or the remains of plants and animals are pressed and cemented together.
Term
Sedimentary rocks are formed in ____________ and buried ________________.
Definition
layers & below the surface
Term
Metamorphic rock formed when and existing rock is changed by any of three things.  What are they?
Definition
  1. Heat
  2. Pressure
  3. Chemical reactions
Term
Where do most metamorphic rock form?
Definition
Most metamorphic rock forms deep underground.
Term
Gneiss is a kind of rock that forms when what happens?
Definition
When heat and pressure inside Earth change granite.
Term
The name igneous come from what Latin word & what does it mean?
Definition

It comes from ignis and it means fire.

 

Term
What is extrusive rock?
Definition
It is igneous rock formed from lava that erupted onto Earth's surface.
Term
What is the most common extrusive rock? 
Definition
Basalt
Term
What forms much of the crust, including the oceanic crust, shield volcanoes & lava plateus?
Definition
Basalt
Term
Igneous rock that formed when (1)_________ hardened beneath the earths surface is called (2) ___________.
Definition
  1. magma
  2. intrusive rock
Term

What does the texture of an igneous rock depend on?

What are the only exceptions to this rule?

Definition

the size and shape of its mineral crystals

The only exception to this rule are the different types of volcanic glass - igneous rock that lacks a crystal structure.

Term
Igneous rocks may be similar in mineral composition and yet have very different textures.  Why?
Definition
Rapidly cooling lava forms fine-gained igneous rocks with small crystals.  Slowly cooling magma forms coarse-grained rocks with large crystals.
Term
Why type of rock has larger crystals?  Intrusive or extrusive?
Definition
Intrusive
Term
What is the texture of extrusive rocks like?
Definition
They have a fine-grained or glassy texture.
Term

What type of rock is Basalt?

What size are its crystals?

Definition

Basalt is a fine-grained extrusive rock?

The crystals are too small to be seen wtihout a microscope.

Term
Describe Obsidian?
Definition
Obsidian is an extrusive rock that cooled very rapidly without forming crystals.  As a result it has the smooth, shiny texture of a thick piece of glass.
Term
Describe Rhyolite
Definition
A fine-grained, extrusive igneous rock with a mineral composition similar to granite.
Term
Describe Pegmatite
Definition
A very coarse-grained intrusive igneous rock.
Term
Describe Porphyry
Definition
An intrusive igneous rock with large crystals surrounded by small crystals; forms when magma cools slowly at first, then rapidly.
Term
Lava that is low in silica usually forms what?
Definition
It usually forms dark-colored rocks such as basalt.
Term
What does basalt contain?
Definition
It contains feldspar as well as certain dark-colored minerals, but does not contain quartz.
Term
What does magma that is high in silica usually form?
Definition
It usually forms light-colored rocks, such as granite.
Term
What does granite's mineral composition determine?
Definition
Its color - light gray, red, pink or nearly black 
Term
Granite that is light gray with drak specks is rich in what?
Definition
hornblende and dark mica
Term
If there are quartz crystals in granite - what does it add?
Definition
light gray or smoky specks.
Term
What is gabbro?
Definition
Thin slices of a rock that geologists can make.
Term
What did ancient Egyptians use for statues more than 3,500 years ago?
Definition
granite
Term
About 600 years ago, the Incas of Peru carefully fitted together great blocks of granite and other igneous rocks to build what and where was it?
Definition
They built a fortress near Cuzco, their capital city.
Term
In the US during the 1800s and nearly 1900s, granite was widely used to build what?
Definition

Bridges

Public buildings

Paving streets with cobblestones

Term
What is granite used in today?
Definition

Curbstones

Floors

Kitchen counters

Term
What is crushed to make gravel that is used in construction?
Definition
Basalt
Term
What type of rock is pumice and what is it used for?
Definition

It is an igneous rock.

The rough surface of pumice makes it a good abrasive for cleaning and polishing.

Term
What type of rock is obsidian & what has it been used for?
Definition

Igneous rock.

Ancient native Americans used obsidian to make sharp tools for cutting & scraping.

Term
How is Perlite formed?
Definition
It's formed from the heating of obsidian and is often mixed with soild for starting vegetable seeds.
Term
Describe the jagged peaks, steep cliffs and deep canyons in Badlands National Park in South Dakota.
Definition
They are sculpted in colorful rock that is layered like a birthday cake.  The layers of this cake are red, orange, pink, yellow or tan.  
Term
How were the layers in Badlands National Park formed?
Definition
These rocks formed over millions of years as particles of mud, sand, and volcanic ash were depositied in thick layers.
Term
Tiny sand grains, mud and pebbles along a stream or beach are what?
Definition
They are particles of sediment
Term
What is sediment?
Definition
Sediment is small, solid pieces of material that come from rocks ro living things. 
Term
In addition to particles of rock, sediment may include:
Definition
  • shells
  • bones
  • leaves
  • stems
  • other remains of living things
Term
When do sedimentary rocks form?
Definition
When sediment is deposited by water and wind
Term
Most sedimentary rocks are fromed through a series of processes (4):
Definition
  1. erosion
  2. deposition
  3. compaction
  4. cementation
Term
What is EROSION?
Definition
Destructive forces are constantly breaking up and wearing away, or weathering, all the rocks on Earth's surface.
Term
What are the destructive forces causing erosion?
Definition
  • heat & cold
  • rain
  • waves
  • grinding ice
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