Transcript planet earth - Mr. Shack`s Class

PLANET EARTH
TOPIC 1 - MINERALS
What is a mineral
A mineral is an inorganic, naturally occurring substance.
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Minerals can be elements (pure substances) or compounds (two
or more elements)
All rocks are made of one or more minerals
Classifying Minerals
We can classify minerals using the following methods:
1.
Lustre - The shininess of a mineral
2.
Colour
3.
Streak – The colour of a minerals streak when you scratch it
4.
Cleavage and Fracture – How a mineral breaks
What is a rock
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A rock is a natural material made of one or more minerals
What is an element
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A pure substance that can’t be broken down into simpler parts by
chemical means
TOPIC 2 – ROCKS AND THE ROCK
CYCLE
Igneous Rocks
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Igneous rock forms when hot magma cools and solidifies
Obsidian and basalt (used in BBQ’s) are two types of igneous
rocks
Sedimentary Rocks
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Rocks made from sediment or loose material
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Sandstone and shale are types of sedimentary rocks
Metamorphic Rocks
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Metamorphic rocks are formed when heat and pressure change
the parent rock into a new rock
Schist and marble are types of metamorphic rocks
Rock Cycle
Rocks continue to change in an ongoing process called the rock cycle
Sediment and Soil
Soil is formed by:
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Rock and rock fragments (sediment)
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Plants and animals add organic matter on top of the rock and sediment
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The above combine to form soil
Humus – Dark, nutrient rich soil
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Humus is important in healthy soil
TOPIC 3 – EROSION
Erosion
The movement of rock and mineral grains from one place to another.
Rock and minerals are broken down through weathering
There are three types of weathering:
1. Mechanical Weathering
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Physical break up of rock
Examples of this are freezing and cracking and gravity causing
rocks to fall and break
2. Chemical Weathering
• Break down of rocks and minerals through chemical reactions
• An example of this is through acid rain
3. Biological Weathering
• Break down of rocks and minerals caused by living organisms
• An example of this is when roots grow through rocks and break the
rock apart
The Changing Surface of Earth
Some common causes of change on the Earth’s surface are:
1.
Glaciers – glaciers erode the land by scraping it
2.
Gravity – gravity causes landslides and rock slides
3.
Wind – wind picks up small bits of material that wear down rock by
abrasion
4.
Water – moving water erodes soil and rock
TOPIC 4 – THE MOVING CRUST
Layers of the Earth
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The thinnest layer is the crust and is where minerals and oil and
gas are formed
The mantle is the thickest section – the upper part is solid the
lower is liquid
The outer core is hot and liquid
The inner core is solid...Why would this be solid while the outer
is liquid?
The high pressure of the outer layers makes it solid
Continental Drift
A theory that says the continents have slowly changed positions over time
Evidence for Continental Drift
1. If you look at the shape of the continents, they look as though they once
fit together.
2. Fossils of the same plants and animals were found on different
continents. Therefore it was concluded that the continents must have
been closer together at some time.
3. Scientists also discovered that similar types of rocks were found
on different continents.
4. Coal beds are found on different continents in moderate to cold
weather climates. However, coal forms in areas rich in plants
that are normally found in warm climates. Therefore they must
have been in warmer areas before and moved.
The theory of Continental Drift was made by the scientist Alfred
Wegner
Theory of Sea Floor Spreading
A theory that states that new rock is being produced at the mid ocean
ridges and that rock moves out, away from the ridge.
The Theory of Plate Tectonics
A theory that states that the Earth’s crust is broken up into pieces called
plates. These plates then move on the Earth’s mantle. This is science’s
best theory to explain volcanoes, earthquakes and mountains.
What causes the Earth’s Crust to move
Convection Currents
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A convection current is the rise of warmer materials followed by the
sinking of cooler materials. This happens in the mantle.
Scientists believe this is why Earth’s plates move.
Why Plates Diverge and Converge (subduction)
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Where convection currents heat up, rise and move away you get diverging
plates.
Where convection currents cool, fall and move towards each other you
get converging plates or subduction.
Diverging Plates and Subduction Zones
The Earth’s Tectonic plates move in two different ways:
1.
Molten lava rises to the surface at ocean ridges causing the plates at
ocean ridges to move away from the ridge – This means the plates
diverge here. Where continental plates move away, a rift valley is
formed.
2.
Where the ocean plates hit the continents, they move under the
heavier continental plates – This is called a subduction zone. Subduction
zones occur near the shores of the continents or where one continental
plate goes under another continental plate.