Volcanic Mountains

When you think of volcanoes, which famous volcanoes come to mind first?  Mt. Fuji is one of the best known volcanoes in the world today.  Here is a list of ten of the most famous volcanoes around the world:Mount_Rainier

  • Krakatau, Indonesia – The entire island was obliterated by its 1883 eruption, and sunsets around the world changed color for the next two years.
  • Lassen Peak, California, USA – erupted in 1917, beginning a period of nearly 75 eruption-free years in the 48 contiguous states.
  • Llullaillaco, Argentina/Chile – At more than 22,000 ft, the world’s highest active volcano last erupted in 1877.
  • Mauna Loa, Hawaii, USA – This is the world’s largest active volcano. Its most recent eruption was in 1984.
  • Mt. Fuji, Japan – This famous symbol of Japan last erupted in 1707.
  • Mt. Mazama, Oregon, USA – Crater Lake formed 7,000 years ago when its side blew out and top collapsed.
  • Mt. Pelee, Martinique – In 1902 only two of the 30,000 inhabitants of the adjacent town survived its 1902 blast.
  • Mt. St. Helens, Washington, USA – It gave several days warning before erupting in 1980, yet 57 people ignored experts advice to relocate and lost their lives.
  • Mt. Tambora, Indonesia – The ashes from its 1815 eruption blocked the sun through most of 1816, creating a “year without summer.”
  • Mt. Vesuvius, Italy – The city of Pompeii was buried under its eruption in the year 79.

All volcanoes are formed in the same way, from the piling up of molten rock that has erupted from deep within our Earth.  When molten substrate cools and become solid, the type of rock formed is termed igneous.  Basalt and rhyolite are two examples of igneous rock. There are three major types of rocks on Earth, the other two being sedimentary and metamorphic rock, both found in tectonic mountains.

There are three distinct location types for volcanic formation on the planet. All volcanoes are formed at one of three places:  at mid-ocean ridges, at subduction zones, or at hot spots.

Atlantis Massif - Mid-Atlantic RidgeMid-Ocean Ridges: When two tectonic plates separate, molten rock wells up between the plates.  The molten rock then cools and the plates continue to separate.  Thus the solid material becomes ocean floor and the upbuilding  forms an underwater mountain range.  An example of this type of volcanic formation is the Mid-Atlantic Ridge, the world’s longest mountain system at more than ten thousand miles in length.

Central Oregon Cascades

Central Oregon Cascades

Subduction Zones: A region where two plates collide is called a subduction zone when the edge of one plate is thrust underneath the edge of the other plate.  Melted rock pushes up through the overlying plate in volcanic eruptions.   Subduction Zone mountain ranges can be created along the edge of a continent when a continental crust is atop the overlying plate.  Some examples of this type of volcano are the Cascade Range in Washington/Oregon and the Andes Mountains.  If both colliding tectonic plates are oceanic, then subduction zone mountain formation can result in an island arc.  Alaska’s Aleutian Islands and the Mariana Islands in the Pacific are examples of island arcs.

Hawaii Volcanoes National ParkHot Spots: Hot spots deep in the mantle of the Earth contain molten rock that rises up through the mantle and the overlying tectonic plate, erupting as a volcano.  As tectonic plates move over hot spots, the hot spots actually migrate with the mantle, creating a trail of volcanic mountains.   The Pacific Plate and an underlying hot spot moved gradually to form the Hawaiian Islands.  Volcanic mountain creation over hot spots is a geologic  process that continues today.