The correct answer is Debris washed down from high ranges.
Let's understand the formation and origin of the Bhabar belt step-by-step:
- Geographical Location: The Bhabar is a narrow belt ranging between 8 to 16 km in width, lying parallel to the Shiwalik foothills at the break-of-slope.
- Origin of Material: As rivers flowing from the high Himalayan ranges descend into the plains, their velocity decreases suddenly due to the gentler slope. Consequently, they lose the energy required to carry heavy sediments and load.
- Deposition: As a result of this drop in energy, the rivers deposit coarse sediments, pebbles, cobbles, gravel, and debris washed down from the high ranges at the foothills. This accumulation forms the porous gravel-ridden tract known as the Bhabar belt.
- Characteristic Feature: Because of the high porosity of the pebble and debris deposits, most of the small streams and rivers disappear underground in this belt, re-emerging further south in the Terai region.
Hence, the origin of the material that makes up the Bhabar belt is the debris washed down from the high mountain ranges.
