A Google Earth oblique view of the Santa Cruz and Urucum Plateaus

The Urucum (left) and Santa Cruz plateaus in Brazil could be the best-preserved stretches of rock on the planet’s surface. Credit: Google Earth

Geology

A 70-million-year-old landscape that looks frozen in time

Brazilian mountains haven’t eroded and could be the oldest surface land on Earth.

A Brazilian plateau could be the oldest landscape on Earth.

The Urucum region of southern Brazil lies in the tropics, where high rainfall usually causes rocks to weather away quickly. But a team led by Paulo Vasconcelos at the University of Queensland in Brisbane, Australia, has discovered that erosion there is at nearly a standstill.

The researchers found that iron-rich rocks atop two Urucum plateaus date to around 60 million to 70 million years ago. The scientists also analysed isotopes of helium, beryllium, aluminium and chlorine in the rock to pinpoint how long the surfaces had been exposed. The team found that the plateau rocks had remained exposed for nearly all of their history.

The key is that some of the iron-rich rocks had been cemented together to form a nearly impermeable surface, which persists until this day. If similar processes have affected other locations, ancient landscapes might be preserved elsewhere, waiting to be discovered.