Igneous Rocks

Igneous Rocks Igneous rocks form when molten rock cools and hardens.

Magma or Lava? Magma: molten rock under ground Lava: Molten rock above ground

2 Types of Igneous Rocks Extrusive- cool and harden at the surface - they cool fast so they don’t have time to form big mineral crystals Intrusive- cool and harden under the earth’s surface -they cool slow so they form bigger mineral crystals

Igneous rock formation

Igneous rock formation

Basalt Color- black Made of- lava How formed-extrusive (cooling lava) Other- aa- rough lava pahoehoe- smooth lava

Obsidian Color- black (clear) Made of- volcanic glass How formed-extrusive, cools VERY fast Other – arrowheads, sharp

Red Pumice Color- red Made of- frothy volcanic lava How formed- extrusive Other- bubbles (vesicles), very light weight

Black Pumice Color- black Made of- frothy volcanic lava How formed- extrusive Other- bubbles (vesicles), very light weight

White Pumice Color- grey white Made of- frothy volcanic lava How formed- extrusive Other- bubbles (vesicles), floats

Granite Color- red, white, black, grey, etc… Made of- quartz, many other minerals How formed- intrusive, far under ground so crystals can slowly grow bigger Other- large crystals

Rhyolite Color- grey, pinkish Made of – quartz and other minerals How formed- intrusive Other- small crystals

Igneous Rocks Info Sheets 7 Igneous Rocks Picture on page 83 Name, picture, extrusive or intrusive?, other characteristics 1. Basalt extrusive aa- rough pahoehoe-smooth 2. - labelled 3. - colored 4. - intrusive: cool underground slow 5. : big crystals 6. - extrusive: cool aboveground fast : small or no crystals 7.