The Restless Earth
Discover why earthquakes and volcanoes happen, and why they don't happen in Britain. Did you know that not all volcanoes erupt lava? This part of the museum has examples of different types of volcanic rock and also rocks folded and fractured by earthquakes.
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Ropy Lava When lava from a volcano erupts onto the land its behaviour and form depends upon its chemical composition and how runny or sticky it is. This kind of basalt lava from Hawaii is known as ropy lava because as its flows the surface rucks up into folds, which look like rope. |
| Obsidian This black shiny rock looks like glass and indeed it is a naturally occurring volcanic glass, called obsidian. It forms when lavas rich in silicon dioxide are erupted and cool so quickly that there is no time for any crystals to develop. Over the millennia obsidian has been valued as a material for the manufacture of very sharp tools and weapons such as arrow heads and spear points. Nowadays, it is more commonly used for jewellery. |
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