9There are lots of different igneous rocks because sometimes minerals get mixed in before it hardens. Also, igneous rocks look different depending on how fast they cool.
10If a rock cools quickly, there is no time for large mineral grains to form. If it cools slowly… what do you think?
11Examples of igneous rock: granite This rock must have cooled slowly because of all of the mineral grains in it Hint: Granite sounds like GRAINS!
12This rock is obsidian, it is smooth. Did this rock cool fast or slow?
13FAST!! There wasn’t time for large minerals to form
14What about basalt? It has tiny, tiny mineral grains but it is mostly smooth Yes, this rock must have cooled quickly
15The second type of rock is called: Sedimentary Rock
16Sedimentary rock forms from layers of sediment Sedimentary rock forms from layers of sediment. Sediment is tiny bits of weathered and eroded rock. Sediment can even be once living plants or animals!
17Sediment is rocks and other things that have SETTLED together, like at the bottom of a lake or river Settled = Sediment
18This is weathered rock that has eroded and settled on the ground This is weathered rock that has eroded and settled on the ground. THIS IS SEDIMENT
19Sedimentary rock is made of layers, CAN YOU SEE THE LAYERS??
20For thousands, even millions of years, little pieces of our earth have been eroded--broken down and worn away by wind and water. These little bits of our earth are washed downstream where they settle to the bottom of the rivers, lakes, and oceans. Layer after layer of eroded earth is deposited on top of each. These layers are pressed down more and more through time, until the bottom layers slowly turn into rock.
21Each layer can be a different mixture of sediment.