Geological Processes

The Geological Timescale

The geological timescale (GTS) is a 'calendar' of all of Earth's history, descending chronologically from modern day to the formation of earth. The GTS subdivides all time into abstract units, which are (in descending order of duration): eons, eras, periods, epochs, and ages.

Examples of Geological Processes

We've learned that geological processes shape our planet. What kind of processes are there?

Mantle Convection

To understand mantle convection, you need to know about the crust and the mantle.

The crust is broken up into tectonic plates.

The mantle is heated by the core below it. As it is heated, its density decreases, so it rises towards the crust. But once the mantle has risen, it begins to cool back down and sink, dragging the crust's tectonic plates above it. This circular movement is known as a convection current.

Nonetheless, not all geological hazards are caused by movement of the Earth's interior. Erosion, weathering, and deposition take place on Earth's exterior, driven by biological, hydrological and atmospheric processes.

Erosion

Erosion is the breakdown and transport of rock particles.

There are six causes of erosion:

• Gravity - Bits of land that have been weathered are caused to go from higher to lower ground by gravity eg. Landslides

• Wind - Wind erodes rock and carries away the sand created. This further erodes other pieces of land. eg. Brimham Rocks, North Yorkshire.

• Rain - Rain-splash erosion causes weathered material such as pebbles or soil to become dislodged. Heavy rainfall then carries sediment into streams and rivers. eg. Rain gullies in Black Ven landslide, Lyme Regis, Dorset.

• Glaciers - These are massive rivers of ice heavy ice that flow slowly and erode away big portions of land, depositing the debris at their tip eg. An Teallach, in Ross and Cromarty

• Oceans - Both current and rising and falling tides cause erosion of coastal areas. eg. Newbiggin Cliff near Filey, North Yorkshire

• River - Rivers both erode and build up land. Meanders form when fast flowing water on an outside curve flows faster than water on the inside. The water on the outside has more power to erode and extend that riverbank while slower water on the inside curve deposits material carried by the river on the inside riverbank. eg. the River Forth

Weathering

Weathering is the breakdown of rocks while they remain in their place.

Causes of weathering can be biological, chemical, or physical.

Deposition

Deposition is the laying down of sediment.

Sediment can be transported as various sizes (pebbles, sand, silt, or dissolved in water) by:

• Wind

• Flowing water (rivers, streams, oceans)

• Ice

How Can Geological Processes Cause Hazards?

Firstly, what is a hazard?

A hazard can result in disaster if it causes damage and destruction.

Hazards at Plate Boundaries

Hazards are common at the boundaries between tectonic plates due to the build up and release of pressure.

Earthquakes: an earthquake is a sudden violent shaking of the Earth's surface. Severe earthquakes can cause widespread damage and destruction, sometimes taking thousands of lives.

Tsunamis: these enormous waves are caused by the displacement of a large volume of water. Marine earthquakes or undersea volcanic eruptions have the potential to generate a tsunami.

Volcanoes: a volcano is a rupture in Earth's crust, from which lava, ash, and gas can escape.

Hazards at Coastal Zones

Geological processes such as erosion and weathering are common along the coastline, where the constant movement of water and wind breaks down rocks. This breakdown can lead to sudden mass movement of rock, which has the potential to cause harm.

Rockfall: rock suddenly breaks away from a steep cliff, triggered by weathering, and forms down the slope to form scree.

Mudflows: earth and mud flow downhill over unconsolidated rock. If it's sudden and fast-flowing, it can present a hazard.

Landslide: rock moves rapidly downhill, often mixed in with mud. Landslides are triggered by very heavy rainfall and can cause a threat to people.

What are the Effects of Geological Processes?

Over time, geological processes can create landforms. These features on the Earth's surface make up the terrain.

There are two different ways of organising landforms.

They can be categorised by their physical attributes:

• Slope

• Soil type

• Elevation

• Rock exposure

• Orientation (direction)

Or by the geological processes that created them:

• Wind

• Erosion

• Weathering

• Glacial movement

• Tectonic plate movement

• Deposition

The Himalayas were formed by the collision of the Eurasian and Indian tectonic plates. Unsplash

What is the Importance of Geological Processes?

Geological processes don't just affect rocks and create landforms; they are tightly linked to life and biodiversity. For example, substrate composition plays an important role in determining biodiversity. The underlying rock type influences the species of plants that grow in an area; in turn, this affects the community composition. The properties of underlying rock can also determine drainage and water availability.

As well as impacting biodiversity, geological processes create resources used by humans in their day-to-day lives.

Energy Resources

Most of the world's electricity is generated by burning fossil fuels – the remains of organisms from millions of years ago. Geological processes such as heating, pressure and sedimentation convert the remains into energy-dense fuels.

Coal, a fossil fuel, is formed by geological processes acting on ancient plant remains. Unsplash

Peat bogs are another source of energy. These bogs are dense wetlands filled with partially decayed vegetation. In some parts of the world, such as Ireland, peat bogs are a major energy resource and are burned to heat houses.

Food and Drink

Soil properties and mineral composition influence the plants that can grow in that area.

Drinking water (as well as water for domestic use) originates from sources above and below ground. The sources underground are known as aquifers – water stored in rock layers.

Minerals

Geological processes result in mineral deposits. Some can be useful for humans.

• Fluoride is a naturally occurring mineral added to toothpaste to protect teeth from developing cavities.

• Calcium is a mineral required for healthy bones and teeth, found in dairy products. Originally, calcium is found in the soil and taken up by grass, which is eaten by cows. Over time, calcium builds up in their bodies and milk.

• Minerals such as gold, cobalt, and lithium are used to build computers and smartphones.

I hope that this article has explained geological processes for you. These natural forces shape our planet, creating landforms and useful resources, but these powerful processes can cause hazards that risk human lives.

^{1. British Geological Society, Holbeck Hall, Scarborough, 2022}

^{2. International Commission on Stratigraphy, Geologic time scale, 2022}

^{3. Magnús T. Gudmundsson, Ash generation and distribution from the April-May 2010 eruption of Eyjafjallajökull, Iceland, Nature, 2012}