Dr Helen Czerski begins the series by looking at the anatomy of an avalanche, using shocking eyewitness footage from within an avalanche and CT scans showing the microscopic changes that cause them.

Helen uses eyewitness footage of eruptions, new thermal imagery and high-speed photography to understand the complex processes captured on camera when volcanoes erupt.

Helen examines the hottest natural phenomenon on Earth - lightning. She explains how specialist photography is revealing how lightning travels through the air and high-speed cameras are showing upward lightning.