This image shows a cross section through the earth’s crust and upper mantle showing lithosphere plates (made of the crust layer and the top part of the mantle) moving over the asthenosphere (upper mantle).
Click on image for full size
Old Rocks Give New Clues about Ancient Earth!
News story originally written on July 11, 2002
What was the Earth like a long time ago? To answer this question, some scientists look for very old rocks to find clues. Now they have found rocks in China that are 2.5 billion year old and these rocks have some interesting clues!
These rocks formed during the Archean Age, when the Earth was young. During the Archean there was no ocean and no continents on the Earth. It was a very hot place. After a long time, Earth cooled a bit, and giant plates of rock started to move around the surface of the Earth just like they do today. This is called plate tectonics . Today, plate tectonics is a very important process on Earth. It makes mountains grow high, volcanoes spew lava, and earthquakes rumble.
Scientists want to know when the Earth was cool enough for plate tectonics to begin. They thought that plates started to move about 2 billion years ago. They thought the Earth was too hot for plate tectonics before that time. But the 2.5 billion year old rocks found in China tell a different story.
These rocks formed in the upper part of the mantle layer, underneath a seafloor. They show that a long time ago they used to flow slowly and were able to move the plates of the Earth’s crust that were above them. So, the plates were sliding around long before we thought they could!
Last modified August 6, 2002 by Lisa Gardiner.
Shop Windows to the Universe Science Store!
Learn about Earth and space science, and have fun while doing it! The games
section of our online store
includes a climate change card game
and the Traveling Nitrogen game
You might also be interested in:
The Archean is the name of the age which began with the forming Earth, as illustrated in this picture. This period of Earth's history lasted a long time, 2.8 billion years! That is more than half the...more
Many forces change the surface of the Earth over time. The largest force that changes our planet's surface is movement of Earth's outer layer in a process called plate tectonics. As shown in this picture,...more
It was another exciting and frustrating year for the space science program. It seemed that every step forward led to one backwards. Either way, NASA led the way to a great century of discovery. Unfortunately,...more
The Space Shuttle Discovery lifted off from Kennedy Space Center on October 29th at 2:19 p.m. EST. The sky was clear and the weather was great. This was the America's 123rd manned space mission. A huge...more
Scientists found a satellite orbiting the asteroid, Eugenia. This is the second one ever! A special telescope allows scientists to look through Earth's atmosphere. The first satellite found was Dactyl....more
The United States wants Russia to put the service module in orbit! The module is part of the International Space Station. It was supposed to be in space over 2 years ago. Russia just sent supplies to the...more
A coronal mass ejection (CME) happened on the Sun last month. The material that was thrown out from this explosion passed the ACE spacecraft. ACE measured some exciting things as the CME material passed...more