Desert pavement formed long ago in an area that is extremely flat and arid, where tectonic activity is low and rocks are highly resistant to weathering. A pencil is shown for scale.Earth’s surface is mostly fresh in geologic terms.
Weathering — wind and water, freezing and thawing — takes its toll, and longer-term changes caused by volcanic activity and sliding crustal plates, known as tectonic activity, fold today’s ground into tomorrow’s interior.
The constant makeover of the planet is typically fastest in the mountains, slower in the tectonically inactive deserts.
A new study of ancient “desert pavement” in Israel’s Negev Desert finds a vast region that’s been sitting there exposed, pretty much as-is, for about 1.8 million years, according to Ari Matmon and colleagues at Hebrew University of Jerusalem.
It is the oldest known vast expanse of surface area. In fact it is more than four times older than the confirmed next oldest desert pavement, in Nevada, according to an article at the web site of the American Association for the Advancement of Science.
The newly dated desert pavement does not represent the oldest material on Earth, however. A lot of individual rocks have been found that are much older.
But Matmon’s team dated the entire surface as a “geomorphic feature,” he told LiveScience. “Since the initial formation of desert pavement (the material we dated) is genetically related to the age of the surface we dated the surface itself,” he said. “We did not choose the outstanding anomalous rocks on the surface.”