Plutons

Sill

*Concordant *typically horizontal *forms when magma intrudes by f/w layers of rock and pushes it up

Batholiths and Stocks

*Discordant *Batholiths=>100 Km^2 (40mi^2) of exposed rock *Stocks=100km^2 or less *made of granite and/or diorite *Batholiths form over millions of years by repeated intrusions *Batholiths can cover 10's of 1000's of km^2 *typically form at convergent plate boundaries or over a hotspot.

Dike

*Discordant *vertical or steep incline *forms when magma intrudes into a crack (then cools) *forms when a wall-like mass if it is more resistant than surrounding rock (which eroded) *associated with fissure eruptions> lava shooting up through crack

Laccolith

*concordant *dome-like or lens-shaped *forms when magma pushes up rocks more in the center than the edges *sometimes called a "laccolith dome." ex:devils tower in wyoming

Pluton

A mass of igneous rock formed underground. Also called an igneous intrusive. *can later be exposed by erosion

Massive (Nontabular) Pluton (Pluton Classification)

Any shape besides tabular. Often bulbous or lens-shaped.

Discordant Pluton (Pluton Classification)

Cuts across rock structure

Concordant Pluton (Pluton Classification)

Matches up with the structure of surrounding rocks (layers, etc.)

Tabular Pluton (Pluton Classification)

Slab-like (tablet-shaped). *Can be concordant or discordant