rocks

ROCKS

Igneous Rocks

Intrusive: form when magma cools ___________ inside the Earth.

Extrusive: form when lava cools ___________ on the Earth’s surface.

Texture of Igneous rocks

Intrusive igneous rocks: Cool slowly Allows time for the minerals to

form _________ crystals Rocks with large crystals have a

_____________ texture Example: granite, gabbro

Granite Gabbro

Extrusive igneous rocks Cool _____________ Quick cooling doesn’t allow time for

large crystals to form This produces a ___________ texture

Example: basalt Extremely rapid cooling cause NO

crystals to formExample: obsidian (volcanic glass)

Sometimes gasses are trapped in cooling magma and form bubblesExample: pumice ,scoria

Basalt Obsidian

Pumice Scoria

Igneous Rock Structures

Intrusion: underground rock mass made of intrusive rock

Extrusion: surface rock mass of extrusive rock

Intrusions

Batholith: ____________ intrusion Large underground mass of rock

which may cover hundreds of miles

Laccolith: Magma flows between rock

layers and spreads upward, pushing the rock above into an ___________

Sill: Sheet of magma

________________rock layers and hardens

They are always parallel to the ______________ rock layers

Can be thin (few centimeters) or thick (several hundred meters)

Dike: Forms when magma forces its

way into existing fractures Once magma hardens it is called

a dike Dikes cut ___________ rock layers

(perpendicular to them)

Extrusions

Volcanic neck: Solidified central shaft of a volcano

Lava flow: Erratically shaped mass of extrusive rock

Lava capped-plateau Lava that spreads over vast area and

hardens