Transcript The Rock Cycle - Science A 2 Z

The Rock Cycle
Three Types of Rocks on Earth
Presented by, Jaclyn Memmott
Did you know that rocks are constantly being recycled? Recycle
means to take something old and change it into something new.
So some of these old rocks that have been around for more than
four billion years are being changed into different rocks. Of
course, that doesn't happen over night. It takes millions of years.
To better understand how this happens, let's take a journey
through the rock cycle.
First our journey begins
within the earth…
Here we see some hot
magma (molten rock)
that is being pushed up
towards the Earth’s crust.
Some of this magma
creeps into the cracks of
the volcano; while, the
rest is forced out the top
through the crater cone.
Once the magma is out of
the volcano, it is called
lava.
Igneous Rocks are cool
As the magma pushes towards the earth's
surface, and turns to lava it cools into solid
igneous rock. Magma that cools quickly forms
one kind of Igneous rock (extrusive), while
magma that cools slowly forms another
(intrusive).
Weathering and Erosion
Over time wind, rain, and
sun wear rocks down and
break them apart. The
resulting bits and pieces of
material are called
sediment. Sediment is then
transported by wind and
water, often ending up far
from where it started. These
processes of breakdown and
transport due to exposure to
the environment are called
weathering and erosion.
Compacting and cementing
Over time, sediment is
washed into oceans, lakes,
and valleys and it starts to
build up in layers, weighing
down the other sediment
that is beneath it.
This weight presses the
sediment particles together,
compacting them. Water
passing through the spaces
in between the particles and
helps to cement them
together. This process of
compacting and cementing
sediment forms…
Heat & Pressure

Due to movements in the crust, rocks are frequently pulled
under the surface of the earth, where temperatures increase
dramatically the farther the rocks descend. Below the earth's
surface, temperatures are hot enough to melt most rocks.
However, before the melting point is reached, a rock can
change.
Heat and pressure work together to alter the rocks under
the earth's surface. This kind of change, which results from
both rising temperature and pressure, is called
metamorphism, and the resulting rock is a…
Metamorphic Rocks
Melting

it takes a lot of heat to melt a rock. The high temperatures
required are generally found only deep within the earth. It
takes temperatures between 1,100 and 2,400 degrees
Fahrenheit to melt a rock, turning it into a substance called
magma (molten rock).
The Rock Cycle can
Begin all over again!
References:

http://www.learner.org/interactives/rockcycle/change2.ht
ml

http://library.thinkquest.org/J002289/index.html