Rock and Topography (World Geography)

Marble is a metamorphic rock of limestone. Metamorphic rock is a type of rock that forms when existing rocks (igneous, sedimentary, or even other metamorphic rocks**) are subjected to high pressure, high temperature, or chemical processes, usually deep within the Earth’s crust, without melting.

Key Features:

1. Formed from: Pre-existing rocks (called parent rocks)
2. Process: Metamorphism – change due to heat, pressure, and fluids
3. Texture: Can be foliated (layered) or non-foliated (massive)
4. Hardness: Often harder and more compact than original rock

A rift valley is a linear shaped lowland caused due to a fissure in the earth along which one side move down with reference to the other.

• It is commonly seen between several highlands or mountain ranges created by the action of a geologic rift or fault.
• A rift valley is formed on a divergent plate boundary, a crustal extension spreading apart from the surface.

An archipelago, sometimes called an island group or island chain, is a chain, cluster or collection of  islands. The word archipelago is derived from the Greek language.

Famous Examples:

• Indonesia – World’s largest archipelago (over 17,000 islands)
• Philippines
• Maldives
• Andaman and Nicobar Islands (India)
• Hawaiian Islands (USA)

A lagoon is a shallow body of water that is separated from a larger body of water (usually a sea or ocean) by a barrier such as:

• A sandbar
• A coral reef
• A barrier island

The continental shelf is the submerged extension of a continent that lies under shallow ocean water.

Key Features of the Continental Shelf:

1. Location:

Lies between the coastline and the continental slope

Part of the continental margin

1. Depth:

   • Usually up to 200 meters deep

2. Width:

   • Varies greatly: can be a few kilometers to hundreds of kilometers wide

   • Widest off the Arctic coasts of Siberia and northern Canada

3. Economic Importance:

   • Rich in marine life, oil, natural gas, and mineral resources

   • Important fishing zones

4. Examples:

   • Sundaland Shelf (off Southeast Asia)

   • North Sea Shelf (Europe)

Landforms produced by wave erosion are formed when ocean waves continuously hit the coastline, gradually wearing away rocks and soil. Here are the major coastal landforms created by wave erosion:

1. Sea Cliff

• A steep rock face near the coast formed by the erosion of softer rock layers by strong waves.

2. Sea Cave

• A hollow space in the base of a cliff, formed when waves erode weak parts of the rock.

3. Sea Arch

• A natural arch-shaped opening created when waves cut through a headland.

4. Sea Stack

• An isolated vertical rock pillar, formed when a sea arch collapses.

5. Wave-cut Platform

• A flat, rocky surface at the base of a cliff, formed by the retreat of the cliff due to wave erosion.

6. Blowhole

• A vertical shaft in a coastal rock, formed when waves force water and air through cracks, sometimes causing water to shoot upward.