Rocks and Weathering

Question 1

What types of rock are there?

Answer 1

There is metamorphic rock, igneous rock and sedimentary rock.

Question 2

What is igneous rock?

Answer 2

Igneous rock is rock that has formed out of cooled magma or lava. It is tough, hard and resistant to erosion.

Question 3

What two types of igneous rock are there?

Answer 3

There is intrusive igneous rock, which is when the rock does not rise to the surface, and extrusive igneous rock, which is when the rock rise to the surface and comes out.

Question 4

Give two examples of igneous rock.

Answer 4

Basalt and granite.

Question 5

What is sedimentary rock?

Answer 5

Sedimentary rock is rock made up from layers and layers of debris that sunk to the bottom of the sea, and compressed through pressure into rock. Some are tough and some are weaker than igneous and metamorphic rock.

Question 6

Give two example of sedimentary rocks.

Answer 6

Two sedimentary rocks are limestone and chalk.

Question 7

What is metamorphic rock?

Answer 7

Metamorphic rock was originally sedimentary or igneous rock, but it changed under heat and pressure. It is tough and resistant to erosion.

Question 8

Give example of a metamorphic rock.

Answer 8

Some metamorphic rocks are slate, marble and diamond.

Question 9

What three categories of weathering are there?

Answer 9

There is physical weathering, biological weathering and chemical weathering.

Question 10

What types of physical weathering are there, and how do they work?

Answer 10

There is freeze-thaw, which is when water fills a crack in the rock, and when that water freezes, it expands and the rock cracks into several pieces. There is also exfoliation, which is when in places with large changes in temperature (e.g. deserts), large amounts expansion and contraction take place. The surface becomes the warmest, so it expands and eventually ‘peels off’.

Question 11

What is weathering?

Answer 11

Weathering is the breakdown of rocks without an agent, such as the sea, a glacier or precipitation.

Question 12

What biological weathering is there, and how does it work?

Answer 12

The biological weathering is called Plants and Lichens, and it works because plant roots can get into tiny cracks in the rock, and the roots then grow and open the rock up. Another way is when plants are decaying, they produce acid which can eat away at the rock.

Question 13

What types of chemical weathering are there?

Answer 13

There are three types of chemical weathering: carbonation, oxidation and hydrolysis.

Question 14

How does carbonation work?

Answer 14

Carbonation takes place when carbon dioxide from the air dissolves in rain to form carbonic acid. If the acid attacks calcium carbonate rocks (e.g. limestone), the calcium is removed which can create some spectacular limestone features, such as stalagmites and stalactites.

Question 15

How does oxidation work?

Answer 15

Oxidation, also known as rusting, occurs when oxygen and moisture mix with minerals that contain iron to create rust.

Question 16

How does hydrolysis work?

Answer 16

Hydrolysis occurs when water combines with some minerals in rock and turns them into clay, making them easier to wash away.

Question 17

What three minerals make up granite?

Answer 17

The three minerals that make up granite are quartz, feldspar and mica.

Question 18

How do tors form?

Answer 18

Tors form when there is a large amount of granite, but with some areas having more cracks than others, so when weathering takes place, the areas with more cracks have been eroded more than the area with less cracks. The large blocks left are called tors, and the small fragments make a scree.

Question 19

Where in England are there lots of tors?

Answer 19

A big area of granite in England is Dartmoor in Devon.

Question 20

What are some uses of metamorphic rock?

Answer 20

Diamonds are very hard and strong, so they are used in mining tools to cut through hard objects. They also reflect the light, which makes the ‘shimmer’ and they are very durable which makes them desirable for rings, bracelets, watches and necklaces. Marble is also very sleek and pretty, so it is used in houses, mainly in bathrooms, floors and walls. Slate is very thing and resistant to erosion, so many roof tiles are made out of slate.

Question 21

What uses are there of sedimentary rock?

Answer 21

Limestone is resistant to erosion and tough, so it is used in floors and walls. Chalk, while not being very resistant, is used as crayons to write on blackboards. Clay, when fired in a kiln, is tough and resistant to erosion, so it is often used in pots.

Question 22

What uses are there of igneous rock?

Answer 22

Both granite and basalt are used in kitchens and homes, in surfaces and table-tops. They are also used in tombstones. Obsidian when carved properly is extremely sharp and is often used for blades and daggers. Obsidian was used by the Aztecs for their ceremonial sacrifices.

Question 23

What is the difference between joints and bedding planes in limestone?

Answer 23

Joints are vertical cracks in the limestone, while bedding planes are horizontal cracks.

Question 24

What are swallow holes and sink holes?

Answer 24

Swallow holes and sink holes are both where rivers flow into the limestone. They have both been formed either by the chemical attack of the water on the limestone, or by the collapse of a cavern below. They are nearly identical, except swallow holes are larger

Question 25

How do stalagmites and stalactites form?

Answer 25

Stalagmites and stalactites form when carbonic acid in the water destroys the calcium in limestone. Stalactites are on top of caverns, while stalagmites are below.

Question 26

When was chalk formed?

Answer 26

Chalk was formed 70-100 million years ago.

Question 27

Why is chalk not very water resistant?

Answer 27

Chalk is not very water-proof because it is an example of a porous rock, as it has pore spaces which can hold water.

Question 28

Is clay a porous rock?

Answer 28

Clay is a porous rock, but it becomes impermeable when wet, as the particles fill the pore spaces.

Question 29

What does impermeable mean?

Answer 29

Impermeable rocks don’t allow water to flow through them. Granite is impermeable.

Question 30

What are some positives of quarrying?

Answer 30

Quarries provide lots of jobs in areas where employment is hard to come by, the increased income from the quarry would mean more money in local economy, and good landscaping of quarry when rock is could could enhance the natural beauty of the area.

Question 31

What are the negatives of quarrying?

Answer 31

Noise pollution because of blasting, noise and dust pollution from heavy lorries taking the mined rock, visual pollution from quarry and slag heaps and pollutants from quarry could harm local wildlife.