IGNEOUS ROCKS IN DEPTH

VIDEO LOG: 

WATCH AFTER YOU TAKE THE NOTES!

​

SHE ABSOLUTELY CRUSHES THIS TOPIC!

PAY ATTENTION TO HER!

FOR YOUR NOTEBOOK:

Lesson 6:  Igneous Rocks

Igneous in Depth

Igneous rocks are formed when magma or lava cools!

1. Intrusive vs. Extrusive

   • Intrusive Igneous Rocks - Form in the Earth - Cool Slowly​ - Forms big crystals and mineral grains

     • Examples:  Granite​, Gabbro, Pegmatite

   • Extrusive Igneous Rocks - Form on the Earth's Surface - Cool Quickly - Forms tiny mineral grains

     • Examples:  Pumice, Scoria, Obsidian​

2. Mafic vs. Felsic Magma and Lava

   • Mafic

     • High in Magnesium and Iron

     • Mg and Fe make the rocks formed appear dark

     • Mg and Fe make the lava flow smoothly so these active volcanos are less explosive

     • Forms a lot of the ocean floor (Basaltic Rock)

   • Felsic

     • High in the element Silica and the mineral Feldspar​

     • This makes the rocks appear light in color

     • Silica makes lava sticky which leads to explosive volcanos

     • Much of our earth's surface is Granitic in nature.  

   1. Vesicular vs. Porphyritic vs. Basaltic vs. Andesitic 

      1. Vesicular means that the rocks have a lot of holes in it.  Felsic lava is sticky, so gases escape as the rocks form.  This makes holy rocks like pumice and scoria when launched from a volcano.

      2. Porphyritic means that there are crystals surrounded by fine grain in the rock.  Crystals slowly formed and then the rock was launched from a volcano.  So you have a mix between fine grain and large crystal.

      3. Basaltic means it's fine grained and formed extrusively.  These rocks are heavy and dense.

      4. Andesitic means it's the tweener rock.  It has a mix between felsic and mafic properties.  It's made of intermediate magma.

​

​