Download Unit 3 Lesson 3 Rock Cycle Activity

Grade 9 Geography - Unit 3 Lesson 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 (SiO2). 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.)
There are three types of rocks.
1 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.
2 Sedimentary Rocks - Formed in layers as the result of moderate pressure on
accumulated sediments.
3 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 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
?? interlocking texture of
the grains
?? presence of holes
?? may be dark-colored
and heavy
?? may display two grain
sizes, one
?? much larger than the
other
?? Example -granite
Sedimentary
?? grains cemented
together
?? presence of fossils
?? light-colored and light
weight
??? may display interlocking
grains but
??? very light weight
???
Example sandstone, shale or
coal
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).
hardness
quartz
eye
physical
colouor
SiO2
specific
Grade 9 Geography - Unit 2
Rock Cycle – Word Fill
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 __________________.