Igneous+Rocks

Igneous Rocks

Igneous rocks are formed by heat and fire

 IGNEOUS ROCKS

 * ** Igneous means made from fire or heat. **

**When volcanoes erupt and the liquid rock comes up to the earth's surface, then new igneous rock is made.**

**When the rock is liquid & inside the earth, it is called magma .**

**When the magma gets hard inside the crust, it turns into [|granite]  .**

**Most mountains are made of granite. It cools very slowly and is very hard.** **When the magma gets up to the surface and flows out, like what happens when a volcano erupts,**

**then the liquid is called lava .**

**Lava flows down the sides of the volcano.**

**When it cools & turns hard it is called [|obsidian]  ,** **lava rock** **or  [|pumice]  - depending on what it looks like.** > **The magma comes from the Earth’s core which is molten rock .** > **The core makes up about 30% of the Total Earth Mass (31.5%)** > **It is the only rock that floats.** > **To learn more about igneous rocks and how rocks are formed, take a look at this  [|Volcano WebQuest]  ** || Obsidian
 * ** Igneous rocks form when molten lava (magma) cools and turn to solid rock.**
 * ** Obsidian is nature’s glass. It forms when lava cools quickly on the surface. It is glassy and smooth.**
 * ** Pumice is full of air pockets that were trapped when the lava cooled when it frothed out onto the surface.**
 * **There are** **5 kinds of igneous rocks** **, depending on the mix of minerals in the rocks.**
 * **Granite** **contains quartz, feldspar & mica**
 * ** Diorite contains feldspar & one or more dark mineral. Feldspar is dominant.**
 * ** Gabbro contains feldspar & one or more dark mineral. The dark minerals are dominant.**
 * **Periodotite** **contains iron and is black or dark.**
 * ** Pegmatite is a coarse-grained granite with large crystals of quartz, feldspar and mica.**



Obsidian under a microscope

Basalt



 * Pumice - Very light from lava cooled quickly in water**