close
Anne Casselman
for National Geographic News
for National Geographic News
August 22, 2007
The world's oldest known diamonds have been found encased in a crystal in Western Australia, scientists say (see Australia map).
The minuscule gemstones are 4.25 billion years old and could provide a rare glimpse into Earth's distant geologic past.
"No one would have really predicted that diamonds were in there," said Simon Wilde, a geologist at Curtin University of Technology in Perth and a member of the team that made the find.
The discovery suggests that seas of molten lava that covered primordial Earth had cooled down faster than had previously been thought.
The find also suggests that plate tectonics, the process by which large shelves of Earth's crust move to create geologic activity, may have already been underway.
"A diamond would never form in a magma ocean," said Thorsten Geisler, a geologist at Westfalische Wilhelms-Universitaet in Munster, Germany, and another team member.
The discovery is a shocker to geologists, many of whom believed that the molten lava and volcanic activity persisted on Earth's surface for at least 500 million years after our planet formed some 4.5 billion years ago.
單字
1. encased
To enclose in or as if in a case
2. minuscule
Very small; tiny
3. gemstones
A precious or semiprecious stone that may be used
as a jewel when cut and polished
4. primordial
Being or happening first in sequence of time
5. lava
Molten rock that reaches the earth's surface through
a volcano or fissure
6. tectonics
Relating to, causing, or resulting from structural
deformation of the earth's crust.
7. shelves
Bedrock.
8. magma
The molten rock material under the earth's crust, from which igneous rock is formed by cooling.
9. persisted
To continue in existence
全站熱搜
留言列表
