Download Main Idea: How are minerals identified? Main Idea: What is a rock?

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Main Idea: How are minerals identified?
A mineral:
 Is natural
 Is a solid substance
 Has definite chemical composition
 Has a definite physical structure
 Forms a crystal with a regular geometric shape
 Was NEVER alive
Properties used to identify minerals include:
 Streak - Color of powder left behind when a mineral is rubbed on an unglazed tile
 Fluorescence - Glows under ultraviolet light
 Crystal Structure - Atoms arranged in a certain repeating pattern such as a cube
 Cleavage - Break along a flat plane
 Hardness - determined by comparing scratch ability and using the process of elimination
o A mineral can scratch any mineral with a lower number
o A mineral can be scratched by any mineral with a higher number.
o Minerals are compared using the Mohs Hardness Scale.
Minerals have many uses including:
 Graphite = pencil
 Quartz = glass
 Copper = computer parts
 Iron = steel = paper clips, cars, ships, buildings
 Halite = (rock salt) melts ice
Minerals form in several ways:
 enormous heat and pressure deep in the mantle (example: diamonds)
 water evaporates in limestone caves (example: calcite)
 ocean animals use minerals to make protective shells (example: calcite)
 elements in hot water mix with other elements (example: galena)
How geodes form:
1. A fossil shell is buried in sediments.
2. The interior of the fossil shell becomes filled with water.
3. Water evaporates, leaving mineral crystals on the shell walls.
Main Idea: What is a rock?
Rocks:
 Are made of one or more minerals
 Make up landforms such as mountains
McGuire 2010-2011
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Main Idea: What are igneous, sedimentary and metamorphic rocks?
How does each form?
Igneous Rock:
 Magma cools underground => intrusive rocks
o Cool slowly = large crystals = coarse texture
o Examples: granite, diorite
 Lava cools above Earth’s surface => extrusive rocks
o Cools quickly = small or no crystals = smooth texture
o Examples: obsidian, pumice, rhyolite
Sedimentary Rock:
 Clastic = particles “glued” together = often have layers
o Classified by the size of the particles
o Examples: shale, sandstone, conglomerate
 Chemical = water evaporates and leaves chemicals behind = often have fossils of seashells
o Example: limestone
Metamorphic Rock:
 Other rocks are changed by great heat or pressure
o Great pressure from great depth or plates converging
o Great temperature from great depth, contact with lava or magma
Rocks have many uses including:
 Granite – buildings
 Obsidian – blade tools, jewelry
 Pumice – cleaning products
 Shale and mudstone – construction
 Marble – buildings, sculpture
 Slate – chalkboards, roofs, floors
Main Idea: How can rock change into any other kind of rock through the rock cycle?
The Rock Cycle
 Weathering, erosion and deposition changes any rock into sedimentary rock.
 Melting and cooling changes any rock into igneous rock.
 Increased temperature and pressure changes any rock into metamorphic rock.
The Rock Cycle and Plate Boundaries
 Rock is formed or changed by sediment deposit, movement, stress, heat, and pressure.
 All three types of rock can form where land and ocean plates meet and collide.
 Sedimentary rock forms where sediments build up, usually where rivers end at the ocean’s edge.
 Metamorphic rock forms where plates collide.
 Mountains form from heat and high pressure at convergent boundaries.
 Sedimentary rock can be dragged deep into the crust at convergent boundaries.
 Igneous rock forms where existing rock melts or where plates move apart and hot rock moves
upward.
McGuire 2010-2011
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Main Idea: What is the composition of soil? How does soil form?
How Soil Forms
 The most important factor is weathering.
o Physical weathering = rocks broken into small pieces by wind, water, plants, and ice.
o Chemical weathering – chemicals dissolve the minerals holding rocks together.
 It takes wind, ice, plant roots, and bacteria thousands of years to form a few inches of soil.
Soil Layers:
 Litter = surface litter of leaves and grass (0)
 Topsoil = Minerals, living organisms, decaying plant and animal matter (A)
 Subsoil = Small rocks, very little organic matter (decaying plant and animals) (B)
 Bedrock = becomes soil as it breaks down (C)
 Vary in color, mineral composition, humus (plant and animal remains), and the size of particles.
Conserving Soil:
 Deep rooted grasses were plowed up and shallow-rooted crops such as wheat were planted.
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Effect: Not enough plants to hold soil in place so the winds blew soil away.
Plant soil in strips so crops with shallow roots are planted next to crops with deep roots.
o Effect: Roots hold down soil.
Contour plowing and terracing
o Effect: Prevent water and soil from flowing downhill.
Windbreaks (rows of trees)
o Effect: Prevent soil from blowing away.
Modern farming practices
o Effect: Conserve soil for future generations.
McGuire 2010-2011