What is an underwater mountain range called? Question: What is an underwater mountain range called? Mountain Ranges: Mountain ranges are formed by different geologic processes, tectonic plates being one of them. When these plates move together, they push against each other and move upwards to create mountains. In certain areas, tectonic plates move apart, allowing magma to flow to the surface of the Earth. As it cools, it hardens and can form mountains and volcanoes. Mid-ocean ridges are mountain ranges that are found underwater. Tectonic plates that are underneath the ocean move apart and allow magma to flow through them. As the magma cools, it creates underwater mountains. There are many such underwater mountain ranges. Two of the most well-known are called the Mid-Atlantic Ridge and the East Pacific Rise. Although the majority of mid-ocean ridges are underwater, a small stretch of the mid-ocean ridge near Iceland actually is above sea level. Mid-ocean ridg