Rock Blog Part 1

One of the attractions of museums is they preserve and display things from mysterious parts of the planet that are rarely visited. In this series of blogs, I am hoping to delve deeper into some of the mystery and excitement, the stories behind some pretty innocuous looking objects that might otherwise be overlooked. Rocks for example, may appear boring with crystals only slightly better for getting people to stop and look due to their beautiful colours, shapes and sparkle. The frozen aesthetic of crystals, and the apparent blandness of rocks, belies that they are a product of powerful and violent processes deep within the Earth’s crust. This is a constant reminder that what we eat, sleep, go to work on, play on, get bored, destroy, dream and build on is, and always has been, in constant flux.

“Artist’s concept of collision at HD 172555” by NASA/JPL-Caltech – Licensed under Public Domain via Commons

When the Solar System was created about 4.6 billion years ago from the collapse of a giant interstellar molecular cloud, the Earth remained a super-hot mass of magma. No oxygen was present in the atmosphere, in fact it was only 500 million years ago that it became breathable. Prior to this, the Earth was essentially an inhospitable furnace blasted by a continuous onslaught of meteors. There are no meteors or rocks whatsoever from this time in Earth’s history because they would have been vaporised in the swirling Hadean mass. Meteors were exploded out from the same event that formed the Earth, and so the ones that have been found since the surface cooled tell us Earth’s age. We will come onto meteors in a subsequent blog. However, one theory is that a mighty celestial body, Theia, thought to have been a planet the size of Mars, collided with the Earth on its journey beyond us into the cosmos. Happening shortly (in planetary terms) after the Earth formed, the energy produced from this blow was enough to dislodge a mass of boiling rock large enough to eventually settle into the Earth’s gravitational field, and this formed our Moon. Similarly, but on a very much smaller scale, a piece of the moon dislodged by an asteroid or meteor came to earth as a meteorite and is available to touch now in our Fossils, Planets, Meteorites and Minerals Gallery.

Post by Jennie Trueman


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