Post on 14-Dec-2015
transcript
Volcanoes in our Community
Volcanic and Other Types of Rocks and What Makes Them
Science Std: Geo # 3c
There are 3 main types of rocks
Sedimentary
Metamorphic
Igneous
Mel
ting
There are 3 main types of rocksThese rocks all change from one type into another
SedimentaryRock
MetamorphicRock
IgneousRock
SedimentSilt and Dirt
SedimentSilt and Dirt
Lava andMagma
Pressure
Wea
ther
ing
Wea
ther
ing
Pressure
WeatheringWeathering
Heat a
nd P
ress
ure
Heat and Pressure
MeltingCooling
Melting
All rocks are made from….Minerals that can be described by….
A Chemical Formula
Each mineral has a unique (only one)
combination of atoms
How it Looks And Acts
•Porous (lots of tiny bubble holes called vesicles•Granular (lots of small grain parts)
•Smooth / Rough
•Hard / Soft
•Shiny / Dull•How easily it breaks
All rocks are made from….All Minerals have Crystals
Crystals are atoms and molecules that are grouped and stuck together in a neat pattern
Like toy soldiers lined up, they have a definite pattern that keeps going on and on We’ll talk more
about crystals later….
Let’s look at the 3 types of rocksHow are they formed and look
SedimentaryRock
MetamorphicRock
IgneousRock
First we will look at Igneous Rocks
Lets look at the 3 types of rocksMolten rock (magma and lava) cools and makes Igneous RockSedimentary
Rock
MetamorphicRock
IgneousRock
First we will look at Igneous Rocks
Depending on how fast it cools, it looks very different
If it cools fast, it makes small crystals that you can’t see
If it cools slowly, it has time to make big crystals that you can easily see
Lets look at the 3 types of rocksThere are 2 main types of igneous rocks Igneous
RockExtrusive or Volcanic igneous rocks
They cool quickly
Normally come to the surface
Little or no crystals seen in the rocks (Basalt)
Very few crystals makes the rock look like black glass (Obsidian)
Basalt Igneous Rock
Obsidian Igneous Rock
Lets look at the 3 types of rocksThere are 2 main types of igneous rocks Igneous
RockIntrusive or Plutonic igneous rocks
Cools slowly under the surface of the Earth
Big crystals formed easy to see with eyeSizes and shapes vary widely from boulders to whole mountain ranges
Can only see when lifted up or erosion shows them
Granite
Geode
Quartz
Diamond
Lets look at the 3 types of rocksRegardless of the type of rock…. Igneous
RockThe color of the rock depends on the minerals in the magma
Light colored rocks have high silica content
Darker colors are from iron and magnesiumMedium colored rocks have combinations of light and dark minerals
Dark colored rocks have low silica content and have more iron and magnesium
SedimentaryRock
Lets look at the 3 types of rocksThe next type of Rock is Sedimentary Igneous
RockThere are 3 types of sedimentary
SandstoneMade from sediment only
LimestoneMade from pieces of fossils and sediment
ConglomerateMade from other bits of rock and sediment
MetamorphicRock
SedimentaryRock
Lets look at the 3 types of rocksThe last type of rock is MetamorphicThese can be made by…..
Heat aloneThis is where the rocks
are heated and changed without having a lot of
pressure on them
Heat and PressureThis is where there is both heat and a large amount of pressure to change the
rocks
Limestone
Becomes
Marble
IgneousRock
MetamorphicRock
So where can these rocks form?Igneous rocks come from volcanic eventsBut you don’t have to have an eruption to make igneous rocks…..
Magma Pockets
Magma can rise up and collect in a pocket
The magma can cool and form igneous rocks
It cools slowly so it can make large crystals
Lava on the surface
Lava comes to the surface
On the surface it is quickly cooled by air or
water
So it forms small crystal rocks
MetamorphicRock
IgneousRock
So where can these rocks form?Metamorphic rocks form primarily at plate boundaries.
Convergent Plates
2 plates crush and rub together
High pressure and temperatures change the rocks
They can then work their way up or we can dig down
Transverse Plates
2 plates rub together
Harder to do here because you need heat
to have the change
Unless the transverse boundary is deep, you
won’t get the heat needed
SedimentaryRock
MetamorphicRock
So where can these rocks form?Sedimentary Rocks usually form under water
Sand and silt pile up on the ocean floor
Over time (millions of years) the silt on the top presses down on the silt on the bottom
After a long time, the silt on the bottom presses and cements together into new sedimentary rocks
SedimentaryRock
MetamorphicRock
Where do the rocks go?
All rocks erode and wear away due to water and weather and chemical action
Rocks are subducted at convergent plate boundaries and are melted back into
magma
Rocks under the surface can break apart (fracture) speeding up the erosion
IgneousRock
Eventually, all rocks are recycled into another type of rock