In October 2017 an unusual reddish sky and sun were reported across England. But just what had caused it? The answer surprised many. A combination of smoke from wildfires across Spain and Portugal, along with Saharan dust drawn up from southerly winds from Hurricane Ophelia. The dust caused the shorter wavelength light (usually blue) to be scattered – leaving behind the longer wavelength light (red and orange).

What actually counts as dust and how does it get picked up into the air and atmosphere? In this podcast we speak to Dr Rob Bryant, Reader in Dryland Processes in the Department of Geography at the University of Sheffield. You'll learn more about the global dust cycle and how dryland landforms evolve over time and through climatic changes.

 

Learning activities

Listen to the podcast and make notes on the following questions:

  • How is material emitted into the atmosphere?

  • How does it leave the atmosphere?

  • What happens when dust falls into the ocean?

  • What are the benefits of dust to biodiversity?

  • What is an emphereal lake?

  • How do geographers study dust?

 

Drylands should be thought about as a system. Draw a diagram that displays some of the processes, inputs, outputs and flows of energy and material described in this podcast. Need a refresher on atmospheric processes? Take a look at this explainer video by The Met Office.

 

Dr Rob Bryant discusses how dust from the Sahara fertilises the Amazon Rainforest. Watch this video by NASA to discover more about this process and complete the following questions: 

  • How small are the dust particles?

  • How many quantities of dust leave Africa each year?

  • How much is deposited in the Amazon in Brazil?

  • Describe how this dust fertilizes the Amazon in Brazil

 

In pairs, discuss how dryland landscapes are changing as a result of human interaction – think about your answers in terms of local, national and global changes. You can use the articles below to help develop your arguments.

Explainer: how does Saharan sand end up in the UK? (The Conversation, 2014)

Red sun phenomenon 'caused by Saharan dust', analysis shows (BBC, 2017) 

Red sun spotted in sky over UK as Storm Ophelia whips up dust from Sahara (The Independent, 2017)

NASA Satellite Reveals How Much Saharan Dust Feeds Amazon’s Plants (NASA, 2015)

Featured image: Katie Hawrysh @khawrysh / Unsplash

 

Keywords

Anthropogenic
Change caused or produced by humans

Atmosphere
The envelope of gases surrounding the earth

Evaporation
The changing of a liquid into a gas

Descending air
As air warms, it ascends leading to low pressure at the surface. As air cools, it descends leading to high pressure at the surface

Glacial and inter-glacial cycles
Large continental ice sheets in the Northern Hemisphere have grown and retreated many times in the past. We call times with large ice sheets 'glacial periods' (or ice ages) and times without large ice sheets 'interglacial periods'. Glacial periods are colder, dustier, and generally drier than interglacial periods

Grain size
The diameter of individual grains of sediment

Scattering
The process in which electromagnetic radiation or particles are deflected or diffused

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