2i & j - Weathering and Erosion

What are weathering and erosion

Geological processes that work together to break down (weathering) and transport (erosion) rocks on the Earths surface

Define weathering

The process of breaking down rocks and minerals into smaller particles through physical, chemical or biological means

Define erosion

The process of transporting the weathered material (such as rock particles and soil) from one place to another.

It moves these materials by natural agents like water, wind, ice or gravity

What are the 3 main types of weathering in the Maltese Islands

1. Onion skin weathering/exfoliation

2. Biological weathering

3. Chemical weathering

Explain how onion skin weathering/exfoliation takes place

• This happens when a rock is repeatedly heated and cooled. This happens because

• It is heated during the day so its outer layer expands slightly and cools during the night so the rock contracts.

• This continuous expansion and contraction causes the rock surface to crack and peel off like the skin of an onion

Explain how biological weathering takes place

• Biological weathering occurs due to the action of plants and animals

a) Plants

• Seeds may fall into rocks, where the presence of moisture and shelter allow them to grow into plants and trees. As the roots develop, they gradually force the cracks to widen and the rock to break apart (eventually whole rocks can be broken down into small pieces)

b) Animals

• Burrowing animals like rabbits and earthworms can also help break the rock down.

Name 3 places where biological weathering can be observed

• Places where there is an abundance of vegetation (Buskett and Maqluba)

• Along roads, where plants/trees roots are breaking into the tarmac

• Near the coast, where animals (like limpets) dig into and break the rock

Explain how chemical weathering occurs

• Chemical weathering is the breakdown of rocks caused by a change in their chemical composition.

• It occurs when water, air, or acids react with the minerals in the rock.

• In Malta, chemical weathering mainly affects limestone, which is made of calcium carbonate.

• Rainwater is naturally slightly acidic because it contains dissolved carbon dioxide.

• When this slightly acidic water comes into contact with limestone, it reacts with the calcium carbonate and gradually dissolves it.

What features does chemical weathering form

• caves

• dolines

• garrigue landscapes

What conditions can increase the process of chemical weathering

• high temperatures

• air pollution

• humidity

Explain how caves are formed by chemical weathering & give 3 examples of caves in Malta

• Over time, the continuous dissolving of the limestone creates holes in the rock. Water passes through these holes and cracks and enlarges them, over time forming caves

Examples

• Xerris Grotto

• Ninu’s Cave

• Ghar Dalam

How are dolines formed by chemical weathering. Give 2 examples of dolines in Malta

• As previously mentioned, the continuous dissolving of the rock can lead to the formation of underground caves.

• When the roof of this underground cave collapses, a doline is formed

Examples:

• Maqluba

• Dwejra

How does chemical weathering create garrigue landscapes. Give two places where you can find these landscapes

• Garrigue landscapes formed when slightly acidic rainwater chemically weathered and dissolved the limestone over time, leaving a rocky, exposed surface with thin soil

• Pembroke & Mellieha