Climate

Climate is a key factor that determines the rate of weathering of granite through different temperatures and rainfall.

Did you know?

In Tianzhushan area, the annual rainfall is 190cm and the mean annual temperature is 9.5℃. Which kind of weathering is there?

Temperature’s effect on granite

1.Fall in temperature makes the water in joints or fractures freeze . With its volume expanding, the force generated in this process leads to the expansion of the fractures, which contributes to the collapse and cracking of the granite.

2.The granite is composed of minerals with different expansion rates. The temperature difference between day and night causes the expansion of the spacing among mineral grains, making the surface and interior of the granite crack and peel off, which is conducive to weathering.

3.Chemical and biochemical weathering are stronger in warm and humid climates. Minerals composing granite, such as feldspar and mica are prone to be broken down chemically into clay minerals.

Rock composition

The weathering resistances of different rocks or minerals are not the same; therefore rocks are weathered at different rates and intensity, which contributes to the formation of peculiar peaks and rocks.

Granite is composed of quartz, potassium feldspar, plagioclase, biotite, hornblende and so on.

Weathering resistance: quartz＞potassium feldspar & plagioclase＞biotite & hornblende

Rock texture 

The density and the size of the particles of the rock may have the weathering resistance of the rock. Rocks with loose texture or composed of particles with varied sizes are prone to weathering. Rocks with coarse particles are more easily weathered compared to those with fine particles.

Rock structure rocks with joints or fractures are exposed to weathering factors (such as water, plant roots), facilitating the weathering process.

As a rock is reduced into smaller and smaller particles, its surface area increases but its volume remains the same.