There are three categories of rocks
- _________- molten rock beneath the earth’s surface
- ________- small holes made from solified gas bubbles
- __________- the molten rock that reaches the earth’s surface
- ____________- lava flows out and hardens
- ______________- when magma harderns inside the earth
Igneous Rocks Definition
- Igneous rocks are formed from the solidification (making hard) and crystallization of molten rock.
- This makes the rocks hard, solid and compact.
Two Types of Molten Rocks
- Magma – is the molten rock beneath the Earth’s surface
- Lava is the molten rock that reaches the Earth’s surface
- When magma or lava cools and solidifies it forms igneous rocks
- As the liquid rocks gets harder crystals may form
- This gives the igneous rocks it’s texture
Two types of Igneous Textures
- The texture of igneous rock is dependent (relies) the rate (speed) of cooling.
- Slow cooling bigger crystals
- Coarser (rougher) texture
- Rapid cooling smaller crystals
- When bubbles of gas are in solidified lava there are gas holes called Vesicles
- Igneous rocks that have these holes are said to be vesicular.
Cooling , Temperature, & Pressure
- Cooling is related to both temperature and pressure
- When the temperature drops rapidly or pressure is lessened you are going to have less crystals and a finer texture.
- This is usually with molten rocks closer to the earth’s surface or lava on top of the surface.
What are extrusive and intrusive Igneous rocks?
Extrusive Igneous rocks
- Extrusive – when the lava exits the earth’s
Exit –leave outside
- - since it is cooler and less pressure exists on the surface the rocks are finer and have less crystals.
Intrusive Igneous Rocks
- Intrusive when the magma hardens inside the earth.
- since there is more pressure and heat the deeper you go into the Earth
- the larger the crystals and the courser (rougher) the texture of the rock is
Let’s recap! How do Igneous rocks form Through the solidification and crystallization of magma and lava!
How does magma form? Minerals must be melted Some like mica melt under very low temp and other needs a higher temp to melt
Igneous rock scheme ( ESRT)
- This chart is used to help us identify What type of Igneous rock it is.
Where are igneous rocks found? All over They are in oceans, continental rocks
Felsic High density Graphitic Basalt Low density rocks Mafic Continental Ocean