Rocks & Weathering
By Zach Wallis 8P
The whole world is made up of rocks underneath your feet. There are many different types of rock but every single one is made up of minerals.
What is Weathering?
Weathering happens you can't stop it, but what is it? Well, there are three types of weathering:
-Physical Weathering - This is when physical things, like the weather, break down the rocks.
-Biological Weathering - This is when plants and animals destroy rocks.
-Chemical Weathering - This is when chemicals break down the rock.
When rocks warm up they expand, like anything else. When they cool down they contract, so for example in a desert where it is sweltering in the daytime and freezing in the night the rocks expand and contract all the time. This puts a lot of pressure on the rocks creating cracks. This leads to the rocks breaking apart.
When it rains water enters a crack in the rock. The water freezes overnight and makes the crack bigger. The water thaws out in the morning and freezes again expanding the crack even more. This happens repeatedly until the rock breaks away. The following ideo explains in more detail.
Rain, wind and waves-
When the wind is blowing it carries particles, these particles can wear away the rock. Waves and rain turn the rock to smaller particles and wash it away. This is a very sloww process though.
Burrowing animals such as rabbits can make the cracks in a rock a lot bigger when they dig through them. This greatly accelerates the weathering process
Tree roots can grow through the cracks in a rock and when they grow they expand the cracks and the rocks fall away. Moss and other plants like it grow on rocks and some produce chemicals that can break down the rocks.
Rainwater is naturally acidic because it dissolves Carbon Dioxide. When these raindrops patter against a rock or stone they slowly dissolve the minerals in the rock, this is one of the slowest weathering processes.
When fossil fuels are burnt they release oxides into the air such as nitrogen and sulphur. The water in rain dissolves these oxides and creates acid rain. The process is exactly the same as normal rainwater but it is accelerated immensely by the oxides.
Limestone is most easily weathered out of rocks. This video explores limestone weathering:
This song is catchy and really helps get the message across:
Question 1 -
What does wind do to weather rocks?
A) Carries Particles
B) Blows it away
C) Melts it
Question 2 -
Why does rainwater weather rocks?
A) Because it has fun
B) Because it washes it away
C) Because it absorbs oxides
Question 3 -
What is the process of Freezing and melting called in weathering?
Question 4 -
Which of these animals contributes to biological weathering?
B) Sea Cucumber
Question 5 -
Which rock is most easily weathered?
1 - A
2 - C
3 - A