Mountain ranges on Earth are buried in the mantle of the Earth. They are able to rise our of the crust because the "root" of the mountain receives support under the surface by the rocky (Earths crust is made of rock, not water) but pliable (it is also warm and flexible) mantle beneath the surface. The process is somewhat like that of an ice cube floating in water in which the tip of the ice cube (or iceberg in the open sea) which rises above the surface is much smaller than the portion which is below the surface. The portion below the surface we can call a "root". If the material in which the root is floating is strong enough, it can allow more of the tip to rise above the surface.
This phenomenon of low heights of mountanous features on Europa suggests that there might be a process at work whereby the strength of the underlying material is not sufficient to raise mountains up to large heights. Notice that if true, such a process would require the presence of a weak subterranean layer or ocean.
You may leave the tour and read more about the process of erosion, the process of mountain building, or the qualities of the Earth's mantle by using the links found at the bottom of this page.
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