The Gheralta Mountains are in Tigray Province of northern Ethiopia, the northern part of the East African Rift Valley.
In the side of some of these mountains are more than 30 Orthodox cave churches from the 9th to 12th centuries.
They are situated at the geographic and cultural centre of both the northern Aksum culture and the later Lalibela society further south.
The rift is within the Africa tectonic plate itself, splitting into two along a north south line that began about 20 million years ago. This rifting process is forming a Somali Plate and a Nubian Plate.
The churches are looking to the future when the new plates, which are separating at a rate of about 1cm a year, will eventually break away from one-another. This is the same process of sea-floor spreading found at mid-ocean ridges, and will eventually cause the more eastern Somali Plate to break off and a new ocean will form.