Section 3

• Igneous Rock Features

http://canarygeog.canaryzoo.com/Rocks Rocks.htm

Batholith

• Large, intrusive igneous rock

• Often granite or felsic composition

Sill

• Intrusive igneous rock forced between other layers

• Parallel to pre-existing layers

Edinburg--Salisbury Crags

Dike

• Intrusive igneous rock forced between other rock

• Cuts across other rocks

Laccolith

• Intrusion between layers of sedimentary rock

• Often mound shaped at top

Volcanic Neck/Plug

• Magma that cooled in conduit of volcano

• Exposed by erosion of volcano

Rhumsiki Peak, Cameroon

Problem

• Applying Math p 346

• Classifying Igneous rocks

• 3 types of igneous rock based on silica content:– Granitic: More than 66%– Intermediate (Andesitic): 52%-66%– Basaltic: 45%-52%

• A 900 kg block of igneous rock contains 630 kg of silica. What is its classification?

• What we know:– Total rock: 900 kg Silica: 630 kg

• Equation:– Percent = (Mass silica / Mass total) x 100

• Put numbers in:– Percent = (630 kg/900 kg) x 100

• Solve:– 70% so it is _____________________