hardest o
minerals
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Exercises
1.
Tick() the correct option.
1. Which of these sentences is not true for minerals?
They are natural substances
They are formed of crystals
They are made from living things like plants
They are in solid state
2. Which of these is not true for gemstones?
They are pure minerals
They are precious
They are part of rocks
They are expensive
3. What is an igneous rock?
A rock that is formed when magma cools
A rock formed from existing rocks
A rock formed from sediments of rocks
A rock that is man-made.
Where are metamorphic rocks formed?
On the surface of the Earth
On river banks
Deep inside the Earth
n on the ocean floor
n rock) cools
agments of existi
a lake
sedimentary roo
ature and pressur
he Earth's surfa
Answers
Answer:
Explanation:
hapter 4 Rocks and Minerals
Chapter 4 focuses on Rocks and Minerals, looking at types of rocks.
Lessons included in this chapter:
#10 Rocks
#11 Minerals
#12 Igneous Rocks
#13 Sedimentary Rocks
#14 Metamorphic Rocks
Resources for Teachers can be found under the Chapter #4 Copymaster.
Select from the options on the right to proceed.
Rocks Lesson #10
The Earth was formed about 4.6 billion years ago. The planet was so hot that the entire Earth was molten or liquid. As the Earth cooled, the lightest materials floated to the top and the heaviest materials sank to the center. The outer part of the Earth, the crust, consists of the lightest rock.
Rock Lesson - lava flow
The lightest rocks form the continents, which are made mostly of the rock granite. Most of the granite on the continents has, over millions of years, been broken down, transported, and deposited into sedimentary rock. These layers of sedimentary rock vary from 8-9 miles thick to nothing in some areas like the Canadian Shield of North America. The Canadian Shield has huge outcroppings of granite right on the surface. Under the thick layers of sedimentary rock lies the denser granite.
The granitic continents ride on a much denser rock called basalt. These basalts form the bottom of our continents and the bottoms of our great oceans. This layer of rock extends down to 40 miles from the surface of the earth.
Rock Lesson - Lithosphere
The crust is very thin in comparison to the other layers of the earth. The crust is only 3 miles thick under the oceans and about 40 miles thick under the highest mountain chains. The layer of the earth under the crust is called the mantle. It is over 1800 miles thick!! The crust and the upper level of the mantle form a layer of the earth that moves very slowly (1-4 inches per year). This layer that moves and causes earthquakes and volcanoes is called the Lithosphere.
Rocks are made of two or more different minerals that have been:
1. cemented together, or
2. squeezed and heated together, or
3. melted and cooled together.
Rocks make up the majority of the Earth's crust. One of the most common rock is granite. The four minerals that make up granite are feldspar, quartz, mica, and hornblende. Granite was formed when magma cooled slowly forming crystals of the four minerals that make up the rock granite.
Rock Lesson - Granite 1
Look at the photo above of granite. Notice the different mineral crystals that make up the rock, granite.
Most of the Earth's surface rocks are covered by soil or clay. Soil contains very small crushed pieces of rock and organic (plant and animal remains) material. Plants such as grass and trees grow in this region of the crust.
Rock Lesson - Hawaii photo
The photo above shows a recent eruption of ash that has covered and burned an area of dense vegetation in Hawaii. The lava has cooled and is now a volcanic rock called basalt. The weathering process will break the basalt down into small, finer pieces of rock called soil. This process can take a few years or thousands of years to produce soil fine enough for plants to grow well in. The soil will become fertile when bacteria decomposes plant and animal material adding nutrients for living plants.
Rocks are produced in a variety of ways and have been cycled in some area many times. This cycling of the rocks is called the rock cycle.
Rock Lesson - Rock cycle
The rock cycle shows how the earth's rocks are changed again and again. The rocks can be changed at times to another type of rock. The rock cycle can begin anywhere in the cycle. Lets start with igneous rocks. Igneous rocks start as magma. The magma (molten rock under the surface) and lava (molten rock on the surface) hardens into igneous rock. The igneous rock then breaks apart over time through the process of weathering. These bits of broken rock are washed away by rains and deposited in a river. These pieces of igneous rocks are cemented together with other bits of rock and form a sedimentary rock called conglomerate. Over time sedimentary rocks can be buried by earthquakes or other geologic processes. Being buried deep under the surface in areas of high temperatures and pressures or coming in contact with magma can cause these sedimentary rocks to change to metamorphic rocks.
Answer:
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