LESSON OBJECTIVES
Name atleast five (5) rock forming processes.
Define accurately the rock forming processes.
Label accurately the rock cycle.
Explain with the aid of diagram the rock cycle and the rock forming process.
Create a model of a sedimentary rock and then change the rock to igneous
using knowledge gained about rock formation.
3.
What is theRock Cycle?
The rock cycle is the process by which rocks of one kind change into rocks of another
kind.
TYPES OF ROCKS:
There are three main kinds of rocks:
◦ igneous rock,
◦ metamorphic rock, and
◦ sedimentary rock.
Each of these rocks can change into the other kinds by physical processes.
◦ Cooling
◦ Weathering and erosion,
◦ Compacting and cementing,
◦ heat and pressure (metamorphosis),
◦ Melting
4.
The Rock CycleProcess
1. The rock cycle begins with molten rock. Molten rock
is called magma when it is below ground, and lava
when it is above ground. When magma cools and
hardens, it forms igneous rock. This process is called
cooling or solidification or crystallization.
2. Weathering and erosion, break the original rock into
smaller pieces. The smaller material is called sediment
and is carried away (transported) by rivers, wind, and
glaciers and deposited elsewhere. These sediments can
then be buried and hardened (called compaction and
cementation) forming sedimentary rock. This process is
called lithification.
5.
3. Sedimentary rockcan be deeply buried and be
exposed to heat and pressure, which over time, cause
it to change its structure into metamorphic rock. This
process is called Metamorphism, which means
change.
4. Eventually, these metamorphic rocks may be heated
to the point where they again melt into magma and
the process or cycle starts again.
12.
TYPES OF ROCKS
Rocksare not unchangeable! Rocks undergo
changes of form in a rock cycle.
A metamorphic rock can become an igneous
rock, or a sedimentary rock can become a
metamorphic one.
Rocks change very slowly under normal
conditions.
13.
Three types ofrock:
Igneous rocks are formed
when hot magma (melted
rock) is rapidly cooled. Granite,
obsidian, and pumice are all
common examples of igneous
rocks.
14.
Sedimentary rocks areformed by layers of
sediment (dirt, rock particles, etc.) being
mixed and compressed together for
extended periods of time. Common
examples of these rocks are limestone,
sandstone, and shale. Sedimentary rocks
often have lots of fossils in them because
plants and animals get buried in the layers of
sediment and turned into stone.
15.
Metamorphic rocks area
combination of rock types,
compressed together by high
pressure and high heat. They usually
have a more hard, grainy texture than
the other two types. Schist, slate, and
gneiss are metamorphic rocks.
16.
THE ROCK CYCLE
Theserocks change over hundreds of years in the five
steps of the rock cycle:
(1) Weathering & Erosion:
Igneous, sedimentary, and metamorphic rocks
on the surface of the earth are constantly being
broken down by wind and water. Large rocks are worn
down to small particles. When the particles are
broken off a rock and stay in the same area, it is called
weathering. When the particles are carried
somewhere else, it is called erosion.
17.
(2) Transportation &Deposition:
Eroded rock particles are carried
away by wind or by rain, streams,
rivers, and oceans. As rivers get
deeper or flow into the ocean, their
current slows down, and the rock
particles (mixed with soil) sink and
become a layer of sediment.
18.
(3) Compaction &Cementation
(Lithification):
As the layers of sediment stack up
(above water or below), the weight
and pressure compacts the bottom layers.
Dissolved minerals fill in the small gaps
between particles and then solidify,
acting as cement. After years of
compaction and cementation, the
sediment turns into sedimentary rock.
19.
(4) Metamorphism:
Over verylong periods of time,
sedimentary or igneous rocks end up buried
deep underground, usually because of the
movement of tectonic plates. While
underground, these rocks are exposed to high
heat and pressure, which changes them into
metamorphic rock. This tends to happen where
tectonic plates come together: the pressure of
the plates squish the rock that is heated from
hot magma below.
20.
(5) Rock Melting:
Metamorphicrocks underground melt to
become magma. When a volcano erupts, magma
flows out of it. (When magma is on the earth’s
surface, it is called lava.)
As the lava cools it hardens and becomes igneous
rock. As soon as new igneous rock is formed, the
processes of weathering and erosion begin, starting
the whole cycle over again!
21.
CLASSWORK
Write the definitionfor the following rock forming processes:
1) Cooling (solidification/crystallization)
2) Weathering
3) Compaction
4) Metamorphism
5) Melting
Editor's Notes
#19 (Tectonic plates are large sections of the earth’s crust that move separately from each other. Their movement often results in earthquakes.)
