THE ROCK CYCLE
the elements that form the
how elements combine to make
how minerals combine to make
the three major types of
the rock cycle
must read on your own and understand the basics
|The most common elements in the earth
are oxygen, carbon, iron, nitrogen, silicon, and magnesium.
- 90% of earth is iron (33.3%), oxygen
(29.8%), silicon (15.6%), and magnesium (13.9%).
Most iron (33.3%) is in the core
(13.9%) is in the mantle
(46.6%) andsilicon (27.7%), compose almost 75% of the mass of
the crust. aluminum (8.1%), iron (5%), calcium (3.6%), sodium (2.8%),
potassium (2.6%), magnesium (2.1%), and all others (1.4%).
MINERALS MADE FROM ELEMENTS
1. is naturally occurring
2. made of inorganic materials
3. has a definite chemical compound
4. has a definite crystalline structure
MINERALS ARE CLASSIFIED AS:
|A. silicates (SiO4=)
silicon and oxygen
halide (F-, Cl-, Br-, I-)
gold, silver, copper, carbon (diamond
or graphite), and sulfur.
HOW MINERALS ARE FORMED
ROCKS are aggregates
or mixtures of various MINERALS "cemented" together.
Rocks are classified into
The oldest known rocks are about 3.8 billion
|IGNEOUS rocks are created by the
cooling of magma. There are two main kinds of igneous rocks:
- Granites make up much of the continents
and are commonly used for buildings and monuments. They are lighter
and tend to ride up at subduction zones avoiding being recycled. This is
one reason continents have gotten larger over time.
- Basalts are heavy and dense and form
the ocean basins
- Basalts and granites are both very firmly
cemented and strong
- are formed by deposition of eroded
- the kind of sediment depends on the
kind of rock that was deposited
The layered walls of the Grand Canyon
The White Cliffs of Dover are sedimentary
limestone (chalk) deposit formed largely from the shells of marine animals.
- limestone (from carbonates, shells)
- shale (from aluminum oxides or
- sandstone (from sand, silicates)
- These are the softest type of rocks
- are partially remelted igneous or sedimentary
- Marble formed from limestone
- Slate formed from shale
(clays, aluminum oxides) deposits
- Quartz from sandstone
(silicates aka sands) deposits
- These are intermediate in strength, harder
than sedimentary, softer than igneous
found in Greenland, northeastern Canada,
and Australia and are metamorphosed granites.
|The change from one type
of rock into another is called the ROCK CYCLE.
WEATHERING and EROSION
– is when large chunks of rock is
broken into smaller pieces
mechanism is weather, chemical, and biological
||- ice is most common and has the biggest
impact on rock through freeze thaw cycles (potholes in spring)
||– the minerals in rocks reacts with oxygen,
carbonic acid (H2CO3) and water.
- acidic waters will dissolve some minerals
which weakens the structure of the rock (rotten granite)
- it is what causes limestone caves such
as Mammoth Cave in Kentucky or Carlsbad Caverns in New Mexico
- acid waters drip, drip, drip thru the
limestone dissolving minerals which redeposit on the inside of the cave
walls, ceilings and floors.
||– the greatest is tree roots which can
split the rock right off a cliff, especially in combination with expanding
- however, caves have now been show to
be eaten away by certain bacteria that make sulfuric acid that dissolves
– is the movement of rocks and soil
by water, glaciers, by wind, and by gravity
|Earth flows and mud slides occur when
the soil is saturated with water (California)
|Streams and rivers carry large quantities
of sediment that are eventually deposited in the entrance to oceans called
deltas. (New Orleans)
|Glaciers can move rock fragments up to
the size of large boulders. The moving ice and rock further scrapes
gouges the sides and bottom of the glacial valley. If the end of
the glacier occurs on land, the melting ice deposits large quantities of
rock fragments to form a moraine. (Wisconsin)
- The last ice age ended about 11,000
years ago. Glaciers covered much of North America, Europe, and Asia,
including most of Wisconsin.
| Wind can weather rock by sandblasting
it with flying grit and erode rock by picking up small fragments and blowing
them away. When wind blows across dry soil not protected by vegetation
huge quantities of soil are blown away. The "Dust Bowl" of the 1930s
was an episode of this sort.
|Material carried by the wind is deposited
as sand dunes or as extensive areas of fine dust called loess. Loess
has an open porous structure that holds water and it usually contains materials
needed as plant nutrients making it a fertile soil. There are extensive
loess deposits in the central United States.
THE FORMATION OF SOIL
SOILS are a mixture of
1. small rock fragments (really tiny,
sand and clay)
2. organic material
And Building Your Soil
this article must be read
What are MINERALS?
Why do elements combine to form minerals?
Discuss the different ways crystals are
formed, what conditions favor small or large crystals?
What happens when magma is cooled extremely
How are obsidian, pumice or typical lava
rock formed? Why do they look so different?
What are rocks?
Discuss the 3 classification of rocks,
how they are formed and give an example of each.
How is marble formed?
How is shale formed?
How is quartz formed?
How old are the oldest rocks and what
kind are they?
What is the "rock cycle"?
What is "soil", how is it different from
minerals and rocks?
How is "Weathering" different from erosion?
Discuss the main forces that weather rock.
Discuss the main forces that cause erosion
What causes Earth flows and mudslides?
Where is this more likely to occur?
What is Loess?