The Rocks Science
The Rock Cycles
General information about the rocks:
This classification is based on the way the rocks were formed (made) rather than on their structure or appearance.
About 75 percent of rocks on the surface of the Earth are sedimentary, most of the rest is igneous and very little are metamorphic.
There Main Rocks are :
· The word "igneous" is from the Latin that means fire
· Igneous rocks were once hot enough to melt
· he mineral grains in the rock formed very tightly together when they melted and as they cool and they are often crystals
· Igneous rocks are strong and ideal for using in buildings and things like kitchen bench tops that will get a lot of use.
· They are mostly black, white or grey or other colours are pale
· The texture looks like the rock was baked in an oven
· Igneous rocks form in three main places:
where the tectonic plates pull apart (at mid-ocean ridges), where plates come together (at subduction zones) and where continents are pushed together, making the Earth's crust thicker and allowing it to heat to melt
· Once magma erupts as lava, it freezes quickly becoming the igneous rock
· There are often many air bubbles
· Often there are many crystals in the rock like granite
Igneous rocks are formed by lava that slowly cools down and turns into igneous rocks.
Extrusive igneous rock is made from lava released by volcanoes
The air bubbles are easy to see and feel and the rock is light in weight for its size because there are lots of air bubbles all through the rock and this makes it not so dense (tightly packed together).
The layers develop over hundreds and thousands and millions of years. Scientists use these rocks to figure out the date of things they find example: An old piece of pottery discovered could be dated because of the sedimentary.
If the scientists sees particles of dust from a volcano and they knew when it erupted and the dust was in the same layer of the sediment as the pottery they can accurately tell the age of the pottery.
This is the case for all things they find like bones, fossilized plants and animals, minerals and metals like (Gold & Silver) etc.
Sediments on the side of the mountain, it shows all the years from evolution.
There are only two different type of metamorphic rocks and they are:
Metamorphic and non - foliated Metamorphic rocks.