Physical and Chemical Weathering

weathering is the process by which rocks on or near the earth’s surface decay or are broken down

Physical weathering is the breakdown of rocks into smaller particles called regolith by physical forces

there are two types of physical weathers; freeze thaw action and exfoliation

I will discuss the process of freeze-thaw action

Freeze thaw occurs in cold of upland areas where land reaches above and below freezing point

During the day it rains, rain fills the cracks in broken rock up in the mountains

At night, when temperatures are below 0 degrees the water in the cracks freeze and expands

It expands usually around 9-10%

The force of expanding ice is 110kg squared

As it expands it puts pressure on the rock forcing the gap to widen

when it melts during the day the pressure is released

This repeats over time and widens the gap

Eventually the rock breaks off as it is weakens over time

The broken pieces are called scree

Due to gravity they fall down the hill and collect at the bottom of the slope

Scree can be seen in areas in Ireland such as Croagh Patrick during winter

The best conditions for freeze-thaw action are an adequate water supply, rocks with joints (e.g limestone) and temperatures that rise and fall below freezing point

Carbonation is a form of chemical weathering

This is the decomposition of rocks due to the way the minerals react in contact with water

Carbonation occurs when gas in the air (CO2) mixes with rain water and dissolves minerals found in some rocks

Rain water absorbs CO2 in the air

As it passes through the soil it absorbs more CO2 from organic waste