Pahoehoe



Smooth, slow-moving streams of basalt form from the least viscous type of lava – pahoehoe. One of the longest-recorded examples travelled about 50 kilometres after an eruption at Mauna Loa, Hawaii, in 1859. This image captures a lava river from the nearby Kilauea volcano.



(Image: G.Brad Lewis/Aurora/Getty)

A'a



A'a lava also forms from molten basalt. It is thicker and cooler than pahoehoe when it emerges from a volcano, which means that it travels more slowly, creating rough and lumpy blocks of rock. In this picture, taken at Cape Hammond on the Galapagos Islands, a viscous stream of a'a releases plumes of steam as it enters the sea.



(Image: Tui de Roy/minden/NGS) Advertisement

Pillows



When red-hot rock meets freezing ocean, large clumps of lava known as pillows form. Ancient pillow lava found inside 3.5 billion-year-old deposits in Greenland and southern Africa provide evidence that large oceans covered much of the planet at the time. This example of the formations was photographed on the mid-ocean ridge known as the East Pacific Rise.



(Image: Dr Ken Macdonald/SPL)

Spirals



Spiral lava patterns, discovered on Mars in 2012, are created when lava is pulled in two directions at once. This image of Cerberus Palus, a volcanic region of the Red Planet, shows the formation in an area 500 metres wide.



(Image: UA/JPL-Caltech/NASA)

Glassy fibres



Fine glassy fibres up to 2 metres long can form when particles of molten rock are thrown into the air and stretched out by the wind. These strands lie on the surface of a pahoehoe flow at the Kilauea volcano in Hawaii.



(Image: D.W. Peterson/USGS)

Limu o Pele



As molten rock pours into the sea, exploding bubbles of steam can form brownish, green or colourless sheets called Limu o Pele. This flake of glass formed as lava from the Kilauea volcano entered the Pacific Ocean.



(Image: J.D. Griggs/USGS)