Physical geology lecture outline - Igneous Rocks

rock -> naturally occurring aggregate of mineral matter.

Major divisions of rock types:

Sketch of part of Yosemite National Park, deep in the heart of an igneous world, the Sierra Nevada Batholith. Image Source:

How do we tell an igneous rock from a sedimentary one from a metamorphic one?

Igneous rocks in general:

This rock is from a very shallow intrusion in Death Valley. It shows the larger phenocrysts (the larger white and rectangular crystal of feldspar) in the finer grained matrix. Much smaller feldspars also exist. Why the difference in grain size?

Volcanic rocks

What is the magmatic plumbing beneath volcanic activity?

Schematic diagram showing how volcanic rocks and features at the surface are connected to shallow and deeper plutonic rocks and features at depth. Diagram from USGS site:

Plutonic rocks

Image of a sheet like (tabular) intrusion cutting the Madison limestone in Spearfish canyon in the Black Hills. This body is part of a suite of intrusions of Tertiary age found concentrated in the N part of the Black Hills uplift. Devil's Tower is a part of the suite.

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