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