Offshore bar
Also called: Off-shore bar, Bar · Topic: Landforms and their Evolution: Rivers, Groundwater, Glaciers, Waves and Wind · NCERT: Class 11, Ch 6 "Landforms and their Evolution"
Meaning
An offshore bar is an underwater ridge of sand and shingle, which is a mix of pebbles and gravel. It lies in the sea, away from the shore, and runs roughly parallel to the coast. Waves pick up sand from the sea floor and drop it in a line, which builds the bar. Offshore bars are the first line of defence against storms and tsunamis. They make big waves break and lose their force before they reach the shore. If more sand piles up, a bar can rise above the water and become a barrier bar.
Example
Underwater sand bars lie along the low, sandy east coast of India. Where one of them grew above the water, it formed the Sriharikota barrier island off Andhra Pradesh.
Don't confuse with
- Barrier bar: this has risen above the water, often across a river mouth or bay. An offshore bar stays under water.
- Point bar: this is sand laid down on the inner bank of a river bend. Rivers make it, not sea waves.