Laccolith

• In geology, any of a type of igneous intrusion that has split apart two strata, resulting in a domelike structure; the floor of the structure is usually horizontal.
• A laccolith is often smaller than a stock, which is another type of igneous intrusion, and usually is less than 16 km (10 miles) in diameter; the thickness of laccoliths ranges from hundreds of metres to a few thousand metres.
• They can be contrasted with sills, which are sheetlike intrusions oriented parallel to the bedding of the enclosing rock: a laccolith’s ratio of diameter to thickness should be less than 10; a larger ratio would make the body a sill. Acidic rocks are more common than basic rocks in laccoliths.

Batholith

• Large body of igneous rock formed beneath the Earth’s surface by the intrusion and solidification of magma. It is commonly composed of coarse-grained rocks (e.g., granite or granodiorite) with a surface exposure of 100 square km (40 square miles) or larger.
• A batholith has an irregular shape with side walls that incline steeply against the host rock. Most batholiths intrude across mountain folds and are elongated along the dominant axis of the range; faulting and contact metamorphism of the enveloping rock near the batholith is also observed.
• Although batholiths were once believed to extend to unknown depths, recent studies have shown that many of them have a thickness of perhaps 10 to 15 km (6 to 9 miles).