Some signs that a break up is coming aren't always clear cut, but when a rift opens up, it's hard to ignore. This is metaphorically true with relationships, and it's literally true with tectonic plates.

In late March, a combination of heavy rain and seismic activity resulted in a huge tear in Kenya's Rift Valley. The tear, 50 feet deep and 50 feet wide, tore apart the busy Mai Mahiu-Narok road, and split farms and houses apart, according to Face2Face Africa. It's just more proof that in a not-too-distant future, Africa will lose a chunk of its eastern coast.

"Dramatic events, such as sudden motorway-splitting faults or large catastrophic earthquakes may give continental rifting a sense of urgency but, most of the time, it goes about splitting Africa without anybody even noticing," Lucia Perez Diaz, a postdoctoral researcher on tectonics at the University of London, wrote at The Conversation.

Growing apart: How it happens

The Earth is broken up in a series of tectonic plates, pieces of the Earth's crust and uppermost mantle. These plates shift and move above the asthenosphere, a layer of the Earth about 50 and 120 miles (80 and 200 kilometers) below the surface. According to Diaz, we're not sure why the plates moves, but currents within the asthenosphere along with forces between the plates themselves likely contribute to these shifts.

Two of these plates, the African Plate (sometimes called the Nubian Plate) and the Somali Plate, come together as part of the the East African Rift (EAR) system, though both plates are much larger overall. The African plate contains not only most of Africa, but also a sizable portion of the Atlantic Ocean and borders the Antarctic Plate to the south. The Somali plate is centered on Madagascar, and about half of Africa's east coast, from the Gulf of Aden to the north to somewhere near Durban, South Africa sits on the plate as well. The EAR system itself is about 1,800 miles (3,000 kilometers) long.

As these plates move at a rate of 0.24–0.28 inches (6–7 millimeters) a year, rifts form in the land, and these rifts are the initial signs of a continental break-up. Rifts require a great deal of force to happen. After all, they're breaking up the Earth's crust. In the case of the EAR system, a large magma plume in the asthenosphere is pushing up on the mantle and crust, essentially doming it, according to Diaz. This is causing the ground to weak and break apart due to the increase in temperature.

A graphic illustration of a land rift happening due to a rising magma plume. This illustration shows a magma plume rising through the asthenosphere and causing a rift. (Photo: DBoyd13/Wikimedia Commons)

This slow process affords us an opportunity to study the rate at which rifts form, but not all rifts form at the same time or at the same rate. To the south, signs of the rifts are young and volcanic and seismic activity are low, Diaz said. In northern end of the EAR system, however, some rifts began forming 30 million years ago. Diaz explained that some rift valleys in this region are "covered with volcanic rocks. This suggests that, in this area, the lithosphere has thinned almost to the point of complete break up."

When this break does occur, tens of millions of years from now, Somalia and parts of Kenya, Ethiopia, and Tanzania will break apart from Africa and form a whole new landmass.

"The ocean will flood in and, as a result," Diaz wrote, "the African continent will become smaller and there will be a large island in the Indian Ocean composed of parts of Ethiopia and Somalia, including the Horn of Africa.