Columbus understood that the earth is a sphere. He knew about the horizon, navigating by constellations (and the "North Star" in the Big Dipper), and the fact that the position of the constellations changed with the seasons. He had no concern that his ships would "fall off the edge of the earth".
A bit of history how did Columbus described earths shape?
Ellipse.
The tectonic plates below earths surface shape earths landforms
the shape of the earth is not flat. it has a spherical shape. its slightly flattened at the poles to give a nearly spherical shape hence; the earth's shape is better described as a geoid which means the earth's shape
the earths shape and its rotation
Weathering and erosion shape earths surface by changing earths surface by having extreme forces that change earth.
sphere
oval
oblong
by erosion
Round. Most people by the time of Columbus did not believe the Earth was flat, despite what some history books will tell you.
No! pangea changed the sufaces of the earth not the shape