Figure 8: Various intrusive landforms formed in volcanic regions

1. Batholiths are long, irregular, undulating and dome-shaped features. They are a large body of magmatic material that cools in the deeper depth of the crust and develops in the form of large domes. They appear on the surface only after the denudational processes remove the overlying materials. They cover large areas, and at times, assume depth that may be several km. These are granitic bodies. Batholiths are the cooled portion of magma chambers.

2. Laccoliths are formed due to the intrusion of magma along the bedding planes of horizontal sedimentary rocks. They are usually mushroom or dome shaped.

3. Phacoliths are formed due to the intrusion of acidic magma along the anticlines and synclines in the region of fold mountains.

4. Lapoliths are formed when magma solidifies in shallow basins into a saucer shape.

5. Sills and Sheets are intrusive igneous rocks usually parallel to the bedding planes of sedimentary rocks. Depending on the thickness of deposits, thinner ones are called sheets while thick horizontal deposits are called sills.

6. Dykes are wall-like formation of solidified magma. These are vertical to the bed of sedimentary rocks. The thickness ranges from a few centimetres to several hundred metres, but the length can be several kilometres.