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Geology - RocksCH 8 PAGE 277
Structure of the Earth
Geology the study of rocks
core inner most area of the Earth
mantle layer below the Earth's crust
crust the outer surface of Earth
This image is on page 278 of Pearson
Draw a simple cross-section in your notebooks – using the following terms.
Igneous Rocks magma molten rock that does not reach the
Earth's surface
lava molten rock reaching the Earth's surface
igneous rocks rocks formed from cooling magma
extrusive igneous rocks igneous rocks that form on the surface of the Earth
intrusive igneous rocks igneous rocks that form below the surface of the Earth
Crystals minerals chemical substances found in rocks
crystal a solid that has a variety of special shapes
interlocking crystals are crystals that have grown into each other
Characteristics of Igneous Rocks
Igneous rocks are usually
1. Hard – because of the minerals they contain
2. Strong – due to the interlocking mineral crystal that have grown into each other and binds them tightly together.
3. Igneous Rocks - Samples
Classifying Igneous Rocks
2 physical factors classify igneous rocks:
Texture – smooth/glassy Vs obvious lumps/crystals
Colour: Dark (more Iron) eg Basalt
Light (more silica, oxygen, aluminium) eg Granite
Extrusive Rocks
Extrusive (surface) rocks cool quickly and have small crystals.
Basalt – small crystals
Obsidian – microscopic crystals – glassy
Many extrusive rocks contain bubbles of gases
Pumice
Scoria
Intrusive Igneous RocksThese rocks are the result of slowly cooling magma below the surface. They tend to have large interlocking crystals. Two examples are granite and dolerite.
Uses of Igneous Rocks
Ch 8.2 WeatheringPearson p 292 Erosion Video
Multiple Weathering simulations – on wiki as well
Weathering - the physical and chemical processes that break rocks down into smaller pieces
Physical weathering - breakdown of rocks by physical process that may involve : changes in temperature, Ice and water, Wind or Plant roots.
Chemical weathering
Chemical weathering - water, or chemicals in the water and air reacting and breaking down rock – eg carbon dioxide dissolves in water creating a mild acid that can weaken some rocks, other acids may come in the form of acid rain (pollution).
Erosion Erosion - removal of weathered rock particles away from the site
of the weathering
Agents of erosion -factors that cause erosion – water, wind and ice
Sedimentation - the process of water or wind depositing eroded rock particles
S4F activity p 292 Sedimentation in a bottle
Soil characteristics Texture –
the size of the particles that make up soil
Pore spaces - the amount of space in the soil that could be filled with air or water
Structure - how well the soil particles join up to form lumps
Water-holding capacity - measure of how much water a particular amount of soil can hold
Permeability - a measure of how fast water enters the soil
Consistency - the tendency of soil particles to stick together
8.3 Sedimentary Rocks
3 types of sedimentary rocks
Clastic sedimentary rocks – Layered rocks, may contain fossils
Chemical sedimentary rocks – limestone caves
Organic sedimentary rocks - coal
8.3 Sedimentary Rocks
Sedimentary rocks - rocks made by sediments being cemented together
Clastic sedimentary rocks - sedimentary rocks made from weathered sediments of other rocks – mud, silt
Chemical sedimentary rocks - sedimentary rocks that form when dissolved materials precipitate from solution
Organic sedimentary rocks - rocks that form by the accumulation of plant or animal debris, which is then cemented together
Fossils - preserved remains of living organisms
Natural cements - chemicals that can flow around sediments in water and then set like cement – includes calcium carbonate, silica, clay, iron quartz.
Clastic Sedimentary Rocks
1. Contain layers – like pages in a book2. The grains do not interlock, but are
glued together3. The rock may contain fossils.4. p 300
Fossils
Chemical Sediments Usually soft, may contain fossils, rare to see any layeringHalite, gypsum and limestone
Organic Sedimentary RocksCan be layered, contain fossils, can be hard or soft - coal.
Uses of sedimentary rocks
Limestone was used on buildings and monuments, but weathers easily due to pollution.
Sandstone – lasts better, outer layer on many historical buildings
Gypsum – used to make plaster and Gyprock
Rock phosphate (guano) – phosphate ferilizers
Coal – energy supply
Bauxite – from near Weipa is refined in Gladstone as Aluminium
Ch 8.4 Metamorphic Rocks
Metamorphic rocks - rocks formed when high temperature and pressure alter existing rocks. Igneous and sedimentary rocks can be transformed into this third category of rock.
Meta – means to change. Morph – refers to form or shape.
Types of metamorphism Tectonic plates - massive plates that make up the earth's crust, move
on the molten/plastic mantle. There is massive heat and pressure within the earth that can deform rock formations.
Regional metamorphism - metamorphism over a wide area below the crust caused by huge movements of the earth's crust
Contact metamorphism - metamorphism by contact with hot magma as it pushes through the mantle and crust. Diagram 8.4.2 P 306
Metamorphic changes
Diamonds are metamorphic – Pure carbon (charcoal) that has been subjected to very high pressure and temperature, changes from a very soft black organic material to the a clear white, crystal that is the hardest naturally occurring substance.
Banded metamorphic rocks
Foliation - process where minerals under pressure become squashed flat and the rock develops layers or bands
Uses of metamorphic rocks
Slate tiles for roofs and pool table tops
Marble for buildings and sculptures
Quartz for stone age tools
The rock cyclep 308