Mountains
Most mountains form when giant slabs of Earth's outer shell, called tectonic plates, collide and crumple the crust upward. Other peaks are volcanoes built by lava. Some rise when a block of crust is pushed up along a crack.
On this page: how mountains are formed, the tallest peak, whether ranges still grow, and why some mountains are volcanoes.
Read the answer below. In Giant, kids talk with characters and keep the adventure going.
Mountains
Earth's outer shell is broken into tectonic plates. They creep. When two plates carrying land crash, the rock in between folds and stacks. That pile can become a range like the Himalayas. India is still pushing into Asia, so those peaks are still in a construction phase. Other mountains form when a plate dives and melts rock, feeding volcanoes. Fault-block mountains rise when a slab is shoved up along a crack. Wind, ice, and rivers carve the shape later. Building is slow. Carving is slow too.
~4 mm/yr
Himalayas still rise
29,032 ft
Everest above sea
2 plates
Typical collision
Lava
Volcanic cone builder
Mount Everest is the highest point above sea level, about 29,032 feet. That is the usual kid answer. Mauna Kea in Hawaii is taller if you start measuring from the seafloor. Most of that volcano is underwater. So "tallest" depends on the ruler. From the beach, Everest wins. From the ocean floor, Mauna Kea is the longer pile.
Yes, some ranges still grow a little each year. The Himalayas rise because the plates have not finished colliding, about 4 millimeters in a typical year. Other ranges have stopped lifting and are slowly wearing down. Ice, rain, and landslides nibble the tops. A mountain is a contest between lift and erosion. Erosion is the wearing away of rock. The score changes over millions of years, not over a weekend.
A volcano is a mountain built from erupted rock. Melted rock, called magma, rises through a weak spot. When it spills out it is lava. Layers of lava, ash, and chunks stack into a cone. The Andes and the Cascades have many of these. Fold mountains are crumpled crust. Volcanic mountains are piled eruptions. Both can be huge. Only one has a hot plumbing system.
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