Geology - Rocks
CH 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
surface
molten rock that does not reach the Earth's

lava
molten rock reaching the Earth's surface

igneous rocks

extrusive igneous rocks
surface of the Earth
igneous rocks that form on the

intrusive igneous rocks
the surface of the Earth
igneous rocks that form below
rocks formed from cooling magma
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 Rocks
These 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 Weathering
Pearson 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 book
2. The grains do not interlock, but are glued
together
3. The rock may contain fossils.
4. p 300
Fossils
Chemical Sediments
Usually soft, may
contain fossils, rare to
see any layering
Halite, gypsum and
limestone
Organic Sedimentary Rocks
Can 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 cycle
p 308