How to Describe How Gravity Is Mechanical Weathering
- 1). Define mechanical weathering for the audience. Mechanical weathering is the breakdown of rock into smaller bits and pieces without a change in its chemical makeup. A process of the rock cycle--the geologic cycle by which rocks can change form over millennia--mechanical weathering results from erosion by water or wind; expansion and contraction from changes in temperature; frost action, where water enters or condenses within cracks in the rock and, upon freezing, enlarges the cracks; exfoliation, where curved sheets of surface material break off of larger rocks; and main force, where plant roots or animals--including man--crush or break the rock by their action.
- 2). Pour a handful of cat litter onto the table top. Pour a small quantity of water on the litter, so that a bit of it begins to wash away, then state the obvious: erosion, by definition, is the result of gravity, acting in concert with water. The water is merely the medium that wears away and carries off particles of the rock.
- 3). Use an analogy: although sandpaper is the agent by which a board is smoothed, the human using the sandpaper is the primary agent in the act of sanding down the board. Likewise, although water or wind is the agent by which mechanical weathering in the form of erosion occurs, gravity is the primary agent.