Picture of the Week
The kind of matter and energy we can see and touch – whether it is in the form of atoms and molecules, or heat and light, only forms a tiny proportion of the content of the Universe, only about 5%. Over a quarter is dark matter, which is totally invisible but whose gravitational attraction can be detected; while over two thirds is dark energy, a force that pushes the Universe to expand ever faster.
19 September 2013
Geology is not just about sterile, lifeless phenomena. The Earth's evolution over time has been driven in large part by life. The oxygen in the atmosphere was not present before life created it, thanks to photosynthesis by primitive algae around 2.5 billion years ago.
Rocks, too, are greatly influenced by life. The white cliffs of Dover are formed of chalk deposited by countless generations of marine organisms in the distant past.
The most famous and most obvious influences of life on rocks, though, are fossils.
This superb specimen of a trilobite is part of UCL's Geology Collections. Trilobites died out around 250 million years ago, though a distant relative, the horseshoe crab, still lives today. Despite being long-extinct, perfectly preserved specimens like these are quite common.
Photo credit: UCL Geology Collections
High resolution image
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Page last modified on 19 sep 13 16:41