Grade 9 Academic Geography - Unit 3
The Rock Cycle
What is the difference between a Rock and a Mineral?
Minerals are homogeneous, naturally occurring, inorganic solids. Each mineral has a definite chemical
composition and a characteristic crystalline structure. A mineral may be a single element such as copper
(Cu) or gold (Au), or it may be a compound made up of a number of elements such as quartz (SiO 2). About
4,000 different minerals have been described.
Properties of minerals - You can tell the differences between minerals by looking for certain properties.
Because each mineral is unique both chemically and structurally, each mineral has its own set of physical,
chemical and optical properties. Chemistry refers to the basic building blocks that the mineral is made of.
Optical properties are the way a mineral looks and what light does when it shines on it. Physical
properties such as hardness and streak can be tested easily.
 Physical properties may be divided into two groups: (1) those concerned with the effects of light
on the mineral, and (2) other tests.
 The tests include colour, luster and diaphany. Luster is the ability to reflect light, while diaphany
means how translucent a material is (i.e., Can you see through it?).
Other Properties of Minerals
 Specific gravity is a measure of each mineral's own unique density and how it compares to the
density of water. The mineral's density is what makes the mineral heavy or light. Some minerals
are very dense, like the native metals copper, silver, or gold, and some are even lighter than
water and will float! Volcanic pumice will float on water.
 Hardness measures how hard the mineral is relative to other minerals. It is called the scratch or
hardness test. Most minerals will not scratch a quartz crystal.
Rocks are made up of one or more minerals in a physical combination. Examples of rocks are limestone,
sandstone, granite and shale. (If you wanted to think of a comparison to food, a mineral would be like
flour and sugar, and a rock would be a cake.)
Three types of rocks
 Igneous Rocks - Formed from the cooling of molten rock. Volcanic igneous rocks formed from
molten rock that cooled quickly on or near the earth's surface. Plutonic igneous rocks are the
result of the slow cooling of molten rock far beneath the surface. The Canadian Shield is mostly
igneous rock
 Sedimentary Rocks - Formed in layers as the result of moderate pressure on accumulated
sediments. Canadian landforms composed of sedimentary rock are the Interior Plains and the
Great Lakes-St. Lawrence Lowlands
 Metamorphic Rocks - Formed from older "parent" rock (either igneous or sedimentary) under
intense heat and/or pressure at considerable depths beneath the earth's surface. The Canadian
Shield has many deposits of metamorphic rock
The interrelationship among the rock types is referred to as the Rock Cycle.
There are four main layers that make up the Earth.
 Inner Core - A mass of iron with a temperature of about 3,800OC. Although such temperatures
would normally melt iron, immense pressure on it keeps it in a solid form. The inner core is
approximately 2,400 kilometres in diameter.
 Outer Core - A mass of molten iron about 2,300 kilometres deep that surrounds the solid inner
core. Electrical currents generated from this area produce the earth's magnetic field.
 Mantle - A rock layer about 2,800 kilometres thick that reaches about half the distance to the
center of the earth. Parts of this layer become hot enough to liquify and become slow moving
molten rock or magma.
 Crust - A layer from 6.5-40 kilometres thick consisting of sand and rock.
The core, mantle and crust of the earth can be envisioned as a giant rock- recycling machine. However,
the elements that make up rocks are never created or destroyed although they can be redistributed,
transforming one rock type to another.
The Recycling Machine
Liquid (molten) rock material solidifies either at or below the surface of the earth to form igneous rocks.
Uplifting occurs forming mountains made of rock. The exposure of rocks to weathering and erosion at the
earth's surface breaks them down into smaller grains producing soil. The grains (soil) are transported by
wind, water and gravity and eventually deposited as sediments. This process is referred to as erosion. The
sediments are deposited in layers and become compacted and cemented (lithified) forming sedimentary
rocks. Variation in temperature, pressure, and/or the chemistry of the rock can cause chemical and/or
physical changes in igneous and sedimentary rocks to form metamorphic rocks. When exposed to higher
temperatures, metamorphic rocks (or any other rock type for that matter) may be partially melted
resulting in the creation once again of igneous rocks starting the cycle all over again. Since most of the
earth's surface is covered by water - molten material from inside the earth often breaks through the floor
of the ocean and flows from fissures where it is cooled by the water resulting in the formation of igneous
rocks. Some low-grade metamorphism often occurs during and after the formation of the rock due to the
intrusion of the material by the seawater. As the molten material flows from the fissure, it begins forming
ridges adjacent to it. If we examine the rock cycle in terms of plate tectonics, as depicted in the figure
above, we see that igneous rocks form on the sea floor as spreading ridges. As the rocks cool, and more
magma is introduced from below, the plate is forced away from the spreading ridge, and acquires a
sediment cover. As shown in the figure, in this case, the oceanic plate eventually "dives" under the
adjacent continental plate. As the oceanic plate travels deeper, high temperature conditions cause partial
melting of the crustal slab. When that occurs, the surrounding "country rock" (existing adjacent rock) is
metamorphosed at high temperature conditions by the contact. The molten material is either driven to
the surface as volcanic eruptions, or crystallizes to form plutonic igneous rocks.
Recognizing Rocks - How Do I Know What Rock I Have?
Type Features Example
Igneous
Sedimentary
 interlocking texture of the
 grains cemented together
grains
 presence of fossils
 presence of holes
 light-colored and light
weight
 may be dark-colored and
heavy
 may display interlocking
grains but
 may display two grain sizes,
one
 very light weight
 much larger than the other
 Example - sandstone, shale
or coal
 Example -granite
Metamorphic
 interlocking texture of large
grains
 layering
 banded light and dark
colours
 "ching" sound instead of a
"chunk"
 sound when tapped
 Example – marble or slate
Task
Use the information in the “Recycling Machine” and “Recognizing Rocks”, draw the Rock Cycle. You
should be able to (1) identify each rock type, (2) draw arrows between each rock type to show the proper
path of the cycle and (3) identify the physical process that is involved for each rock type to form (e.g.,
magma COOLS to become Igneous Rock).
Rock Cycle – Word Fill
hardness
quartz
eye
physical
colouor
SiO2
specific
cake
optical
gravity
natural
sandstone
flour
structure
chemical
4,000
combination
translucent
luster
reflect
one
Mineral – A mineral is a __________________ substance that has its own distinctive crystalline
______________________ and may have its composition expressed with a chemical formula. Some
examples are _______________, calcite, and galena. Quartz has the chemical composition of
____________.
About 100 minerals are relatively common. There have been over ________________ minerals identified.
Rock – A rock usually composed of two or more minerals in some physical _________________________,
although some rocks are composed of only ______________ mineral. Examples of rocks are limestone,
_______________, granite or shale.
One way of describing rocks and minerals is a mineral would be like ___________ and sugar, and a rock
would be a _______________.
To identify one mineral from another, you look using only your _____________ for the mineral’s
__________________, _______________ and _________________ properties. Each mineral is unique
There are three different physical properties (i.e., characteristics you can see): _________________,
__________________ and diaphany. Colour is the different colour or colours of a rock. Luster is the
ability to _____________ light.
Diaphany means how __________________ (i.e., Can you see through it?)
When you compare a mineral's density to the density of water, you are measuring __________________
________________. The mineral's density is what makes the mineral heavy or light.
When you do a scratch test, you are measuring __________________.
Task



Using Page 40 in Making Connections, complete the Rock Cycle figure
Read Pages 40-42 in Making Connections (Rock Cycle) and answer on Page 42 Questions #1-3
Using Making Connections, complete the following information
Rock Type
Magma
Igneous
Sedimentary
Metamorphic
Description / Where commonly found in Canada