Science 7Discovering Science 7

Unit 4“Earth’s Crust”

Chapter 10

Earth’s Crust Is Made Up Off Rocks And Mineral.

Minerals vs. Rocks• Minerals –

A mineral is a pure substanceex. Gold

• Rocks – A rock is a mixture of two or more minerals.ex. Granite

Mineral/Rock Identification• Lustre – how light is reflected of the material (Dull, Glassy or

metallic).

• Colour – Spectrum of colour.

• Hardness – Moh’s Hardness Scale (1 softest ex. Talc and 10 hardest ex. Diamond).

• Streak – Residue left after a rock is streak across porcelain

(powder,…) • Cleavage – Splitting along smooth, flat surfaces called

planes. Ex. Mica

• Fracture – Splitting along rough jagged edges.

Families of Rocks

Igneous, Sedimentary and Metamorphic

Igneous Rock• Intrusive Rock -

Formed when molted rock (magma) cools under the surface of the earth.ex. Granite

• Extrusive Rock – Formed when molted rock (lava) cools on the surface of the earth.ex. Obsidian

Sedimentary Rock• Formed when loose particles, weathered

and eroded away, are compacted together. The extreme pressure and heat help cement the particles together.

• Cementation – Process by which pieces of sediments are held together by another material.

• Layers of sediments form beds.

Sedimentary Rock

Metamorphic Rock• Metamorphic means “changed form”.• Formed when extreme pressure and heat,

or hot fluid changes one type of rock into another.

• The formation of metamorphic rock is a slow process.

• Parent Rock - The type of rock which has been changed into metamorphic rock.

Metamorphic Rock

The Rock Cycle

Many Things Are Made From Minerals and Rocks

• Zippers• Watches• Shirts• Blood• Muscles• Shoes• Detergents

Mineral and Rock Resources• Petroleum and Coal – made from the remains of

once living things.

• Metals – Copper, Zinc, Nickel, iron, …

• Gems – Sapphires, Diamonds, emerald, Amethyst, …

Chapter 11Earth’s Crust Is Constantly Changing.

The Layers of the Earth

The Earth’s Moving CrustAlfred Wegener (1880-1930)

• Paleogeographic Evidence – Shape of Continent- Pangaea- Theory of Continental Drift

• Biological Evidence – Fossils• Geological Evidence – Rocks and Rock Layer• Meteorological Evidence – Climate Change

Wegner’s Theory RejectedWhat caused the platesto move?

Without an answer,some scientist rejectedhis theories.

Today we accept theexplanation of convectioncurrents

Evidence From The Sea Floor• Sonar (Sound Waves)

• Magnetometers (Magnetic Fields)

• Deep Sea Drilling (Core Samples)

Types of Plate Boundaries• Divergent Boundaries

– Pulling apart

• Convergent Boundaries – Pushing together

• Transform Boundaries – Sliding past (J. Tuzo Wilson)

Convection Currents• The driving force that possible causes

plates tectonics (movement of the earth’s crust).* The creation of subduction zones – The area of the crust when one plate is push below another plate.

Earth’s Crust Catastrophe’sEarthquakes

- Seismograph (Seismic Waves)- Bedrock- Richter Scale- Focus and Epicentre

VolcanoesOccur:- areas where plates converge- areas where plates diverge- areas where plates are thin (hotspots)

Mountain Building• Fold Mountains

• Fault Block Mountains

• Volcanic Eruption

The Geological Time ScaleThe Fossil Record – The Origin of Man

“Evolution vs. Creation”Precambrian – formation of the Earth and

appearance of simple life forms.Paleozoic – appearance of more complex life

forms .Mesozoic – appearance and extinction of

dinosaurs.Cenozoic – appearance of humans.

Chapter 12

Soil Is The Living Component Of Earth’s Crust.

WeatheringWeathering is the mechanical and/or chemical

breakdown of rocks.• Chemical

- Acid rain and ground water-Acid actions of organism (animals and plants)

• Mechanical– Ice/Frost Wedging– Plant roots Wedging– Animal Factor – pathways, burrow, …

Erosion

Erosion is the process that loosens and moves weathered rock particles over the earth’s surface.

• Water in motion

• Meteorological processes (rain and wind)

• Geological processes (gravity and glaciers)

Classifying Soil• Soil is a combination of eroded “rocks and

minerals”, “water”, “air”, and “organic material.”

• Humas is material made from breaking down plant And animal remains.

• Texture relates to how soil feels when robbed between fingers.

- Coarse-textured (sandy, gravel).- Medium-textured (loamy).- ne-textured (clay).

Porosity and Permeability• Porosity

The amount of empty space in soil or a rock.

• PermeabilityThe measure of how easily liquids and gases pass through a soil or a rock