Igneous Activity and Volcanic Landforms

Types of Surface Expression of Igneous Activity

• There are two types of surface expressions of igneous activity: intrusive and extrusive
• Intrusive: occurs when magma rises within the crust and cools
• Examples of intrusive landforms: batholiths, domes (laccoliths), dykes, and sills

Landforms of Igneous Intrusions

• Batholith: a massive igneous pluton formed beneath the Earth's surface by the intrusion and solidification of magma
• Batholiths are exposed by denudational processes and sometimes by continental uplift

Types of Igneous Intrusions

• Phacolith: a lens-shaped mass of igneous rocks occupying the crest of an anticline or syncline, fed by a conduit from beneath
• Sill: a concordant intrusion and solidification of molten magma along the bedding planes of sedimentary rocks; sheet-like in shape
• Dyke: a discordant intrusion that cuts across the pre-existing rock bed, mostly along fault lines
• Laccolith: a large blister/igneous mound with a domed-shaped upper surface and a level base, fed by a conduit from below
• Lopolith: a saucer-shaped (concave) intrusion in bedding planes, smaller in size

This quiz covers the different types of surface expressions of igneous activity, including intrusive and extrusive landforms. It includes examples of batholiths, dykes, and volcanoes.