The reason that the Isthmus has risen is because of something called plate tectonics. It may be hard to believe, but the ground we walk on moves. The movement is usually very, very slow, sometimes only 2.5 centimeters (about 1 inch) per year
The outermost layer of the earth's surface, the part we stand on and the seafloor at the bottom of the oceans, is called the crust. The crust is made of huge rock slabs called plates. There are seven large plates and half a dozen small plates on the earth's surface.
Like giant bumper cars in super slow motion, plates move apart, crash together, or slide past each other. At the edges of the plates volcanoes erupt, and earthquakes shake the ground.
The earth's main landmasses, called continents, have been moving for billions of years.