IGNEOUS ROCKS

Igneous means, “() formed” Solid Rock Igneous means, “() formed”

() is molten (liquid) material () the surface of Earth.

MAGMA VS. LAVA Magma – molten material () the surface of the Earth Lava – molten material () earth’s surface

The () cooled and solidified INSIDE Earth into an intrusive igneous rock

Molten (liquid) material at the surface of Earth is called ().

Extrusive rock is also called () rock. The lava cooled and solidified () it exited Earth into an extrusive igneous rock

When () or () cools it () (a fancy word for something becoming a solid). When this happens crystals form. Solidification can also be called (). The rocks crystals are minerals.

The size of the mineral crystals that form in an igneous rock depend on the ( ). As a general rule, the () a rock takes to cool, the () the mineral grains will become. http://www.wwnorton.com/earth/earth/flash/5_1.swf As a result…

COOLED FAST at the surface, so either there are no () or they are so () they are not visible. COOLED SLOW () the surface, so () minerals have time to grow.

Lava exposed at the surface cools very fast so no minerals can grow, it looks () or has (). Earth’s surface Deep in Earth’s crust

If it cools () the surface it grows () mineral crystals but not big enough to see. Earth’s surface Deep in Earth’s crust

As you get deeper into Earth’s crust magma cools slower As you get deeper into Earth’s crust magma cools slower. This allows () crystals to grow. Earth’s surface Deep in Earth’s crust

Really deep in Earth’s crust magma cools really, really () Really deep in Earth’s crust magma cools really, really (). This allows mineral crystals to grow really, really (). Earth’s surface Deep in Earth’s crust

Which is the intrusive rock and which is the extrusive rock? Pop quiz hot shot!!! Which is the intrusive rock and which is the extrusive rock? Extrusive Intrusive Fine grained Large crystals Basalt Granite

Scheme for Igneous Rock Identification Reference Tables page 6 Scheme for Igneous Rock Identification Determining the properties of an igneous rock then identifying it.

HOLD ON A SECOND… What is the definition of texture when we are talking about rocks?

Grain Size

Non vesicular = No bubbles

Bubbles

The mineral crystal size

Where the rock formed Exited Earth

Where the rock formed Inside Earth

Lets see what these words mean.

Contains magnesium & () () colored Dark colored Contains aluminum Contains magnesium & () () colored Dark colored Typical continental rock composition Typical () rock composition

Practice identifying igneous rocks #1

Lets try to identify an unknown igneous rock Use the E.S.R.T. Lets try to identify an unknown igneous rock Observed properties of the unknown rock: 1. Light colored 2. Low Density 3. Fine Grained 4. Non vesicular (No gas bubbles)

4. Non Vesicular (Nogas bubbles) 1. Light colored 3. Fine Grained 2. Low density

All the rock names are located in this area

We need to use texture to narrow it down further Now we have to see where all our known properties meet in the rock name area The rock could be any in the highlighted area, according to color and density We need to use texture to narrow it down further

The texture was fine and non vesicular The only place these two textures match is right here

The correct rock is located in the area where all the properties overlap.

What do we think our mystery rock is? Yup, It is a sample of Rhyolite, an extrusive igneous rock Identifying any other igneous rock works the same way!!!

Now lets take our sample of rhyolite and find out what its mineral composition is.

Here are the mineral composition percentages If you do not know where in the rock rectangle to go, assume it is right in the (). Middle Here are the mineral composition percentages

All of this equals 100% of the rock’s mineral composition.

We now want to find the individual mineral percentages in our sample of rhyolite

We now want to find the individual mineral percentages in our sample of rhyolite 24% Potassium Feldspar

We now want to find the individual mineral percentages in our sample of rhyolite 36% Quartz

We now want to find the individual mineral percentages in our sample of rhyolite 21% Plagioclase Feldspar

We now want to find the individual mineral percentages in our sample of rhyolite 10% Biotite

We now want to find the individual mineral percentages in our sample of rhyolite 8% Amphibole

Now we know the mineral composition of rhyolite is; 25% Potassium Feldspar 38% Quartz 20% Plagioclase Feldspar 9% Biotite 8% Amphibole All the minerals in the rock are accounted for 100%

Characteristics of Igneous Rocks 1. Tightly () mineral crystals (unless it looks glassy).

Characteristics of Igneous Rocks 2. Intrusive Rocks, formed () inside Earth, have visible (sometimes very ()) ().

Characteristics of Igneous Rocks 3. Extrusive rocks, formed () on the () of Earth, will have a () or () texture.