2 Rocks on the surface of the earth are gradually broken down into smaller particles over time. (a) Name this process. [1] (b) State three agents that cause...
Question 1 Report
2 Rocks on the surface of the earth are gradually broken down into smaller particles over time.
(a) Name this process. [1]
(b) State three agents that cause the physical breakdown of rocks. [3]
(c) Explain how the freezing and thawing of water in rock crevices leads to the breakdown of rocks. [3]
(d) Give two ways in which plant roots contribute to the breaking apart of rocks. [2]
Answer Details
(a) This process is called weathering [1]. Weathering is the breakdown of rocks at or near the earth's surface into smaller particles by physical, chemical, and biological agents.
(b) Three agents that cause the physical breakdown of rocks:
- Temperature changes (heating and cooling) [1].
- Water / rain / running water [1].
- Ice / frost [1].
Other acceptable agents: wind, plant roots, and burrowing animals.
(c) The freeze-thaw process works in three stages:
- Water enters cracks or crevices in the rock surface [1].
- When the temperature drops below 0 degrees C, the water freezes and expands (increases in volume by approximately 9%) [1].
- The expansion exerts enormous pressure on the surrounding rock walls, forcing the crack to widen. Repeated cycles of freezing and thawing progressively enlarge the cracks until pieces of rock eventually break apart [1].
(d) Two ways plant roots contribute to breaking apart rocks:
- Roots grow into existing cracks in rocks and widen them as the roots increase in diameter over time [1].
- Growing roots exert physical pressure on the rock, and root tips can penetrate small pores and force rock fragments apart [1].
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