Earth's deep memory is thawing with the Arctic permafrost, degrading records of our ancient world

Permafrost usually hits the news as a hazard, a planetary risk.

When this ice-rich ground thaws, it damages roads and building foundations.

It drains lakes and tips trees into drunken forests.

It releases greenhouse gases that have been locked in carbon-rich soils for thousands of years, amplifying warming and driving further thaw.