Volcanoes worldwide

The third day of creation God said: “Let the waters under the heavens be gathered together in one place, and let the dry land appear….”

In 1910 the German geophysicist Alfred Wegener called that proto-continent Pangaea. In the Triassic geologic era, 200 million years ago lava from deep in the earth pushed the land mass apart forming the continents we know today: Eurasia, Africa, America, Australia and Antarctica. The continental plates of the earth crust are “floating” on the heavier earth mantle that consists of iron and magnesium silicates. They move apart at the speed of 1 to 2 centimeter per year. (That makes 2000 to 4000 km in 200 million years.) At the rifts where the continents were ripped apart the earth crust is weak, giving way to molten material from the core rising up and forming volcanoes.

This archipelago is part of such a rift usually called the Pacific Ring of Fire. Of the 1,500 volcanoes on earth, 75% are located on that ring stretching from here south to Indonesia, over New Zealand, below the Pacific Ocean to South America up north to Alaska along the Aleutians and Kuril Islands to Japan including the northernmost Marianas and back to the Philippines.

The remaining 375 land volcanoes are situated in Eastern Africa, the Mediterranean, Iceland, the Canaries, Cape Verde, and Antilles Islands.

Along the rift in the Mid-Atlantic Ocean many submarine volcanoes spewed material to fill the deep volcanically active valley. They have formed a new ocean floor and a mountain chain of which the five Iceland volcanoes are the protruding tips. The rift goes on between Africa and Antarctica into the Indian Ocean and passing through New Zealand into the midst of the Pacific Ocean where the Hawaii volcanoes are the peaks of the submarine mountain chain.

Tectonic plates also move towards or dive under other plates like India colliding with South Asia pushing up the Himalaya Mountains or Italy pressing against Europe folding up the Alps. Then destructive earthquakes arise along faults of which the 600-mile long San Andreas Fault in California is the most known. A sudden movement along 270 miles of that zone caused the 1906 San Francisco earthquake. Another such fault runs amidst through Manila.

Magma building up below a volcano also causes the earth to tremble but that is locally limited and less destructive.

Volcanoes near big cities like Mexico, Seattle, Naples, Tokyo, Singapore, Jakarta, and Manila are closely monitored, but many if not most of them are in remote little populated places like New Guinea, the Andes, or Congo Republic where fighting warlords scare away scientists.

Some volcanoes after eruption have collapsed into the emptied magma chamber forming a caldera that is hard to recognize. The Campi Flegrei caldera near Naples is hidden in the Mediterranean Sea. It also took the volcanologists some time to recognize the Yellowstone Caldera, Lake Toba and Lake Taupo in New Zealand’s North Island as such. The Samala volcano on Lombok has completely disappeared after eruption and was rediscovered by French scientists in a computer simulation of the adjacent Rinjani volcano.

Indonesia with its 129 active volcanoes is the most endangered nation followed by the Philippines with 21, seven of which are in Negros and seven on Camiguin. Cebu province has none but that does not mean we are safe from that kind of natural disaster. Canlaon from time to time ejects ash and lapilli and Hibok-Hibok erupted in 1951 without warning, asphyxiating 2,000 people with brown bromine gas. They may be dormant but not extinct.

Erich Wannemacher

Lapu-Lapu City