Volcanic landforms are geographical features formed by volcanic activity, categorized into extrusive and intrusive landforms based on whether magma cools above or within the Earth’s crust. Extrusive landforms, like lava flows, ash deposits, and volcanic cones, form when magma reaches the surface and solidifies. Intrusive landforms develop when magma cools and solidifies beneath the Earth’s surface, assuming various shapes.
Types of Intrusive Landforms:
- Batholiths: Large bodies of magmatic material that cool deep within the crust, forming large domes. They surface only after denudation removes overlying materials. These granitic bodies, often several kilometers deep, are cooled magma chambers. Example: Granite batholiths in the Karnataka plateau.
- Laccoliths: Large, dome-shaped intrusive bodies with a level base, connected by a pipe-like conduit from below. They resemble surface volcanic domes but form at deeper depths. Example: Domal hills of granite in the Karnataka plateau, often exfoliated, are laccoliths or batholiths.
- Lopoliths: Saucer-shaped, concave-upward bodies formed when lava moves horizontally along weak planes. They develop where magma rests in a horizontal form.
- Phacoliths: Wavy intrusive rock masses found at the base of synclines or top of anticlines in folded igneous regions. They have a definite conduit to underlying magma chambers, later forming batholiths.
- Sills: Near-horizontal intrusive igneous bodies. Thinner ones are called sheets, while thicker deposits are sills. They form flat layers within the crust.
- Dykes: Wall-like structures formed when lava solidifies almost perpendicular to the ground through cracks and fissures. Example: Dykes in western Maharashtra, considered feeders for eruptions forming the Deccan Traps.
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