|
|
|
  |
| Sunday, 14 November 2004 |
 |
|
 |
Junior Observer |  |
| News Business Features Editorial
|
Volcanoes on the sea bed
The most productive volcanic systems on Earth are hidden under water. These are located under an average of 8,500 feet of water. According to statistics, there are over 5,000 active volcanoes underwater, varying from those larger than any on the surface to those no larger than a car. Beneath the oceans, a system of mid-ocean ridges produces an estimated 75 per cent of the annual output of magma. The magma and lava create the edges of new oceanic plates and supply heat and chemicals to some of the Earth's most unusual and rare eco-systems. Conditions during under water eruptions are very different from conditions during eruptions on land. The water quickly quenches the lava, turning the outer surface of the flow to a glass-like substance. Would you believe that the weight of the overlying water can make the pressure 250 times greater than atmospheric pressure? The pressure is so great that there is great difficulty in forming bubbles in magma and lava. If the global estimate of one million submerged (under water) volcanoes is correct, perhaps thousands of these volcanoes could be active. In contrast, only a few submerged volcanoes are detected in the process of erupting. Of the nearly 8,000 known volcanic eruptions in the last 10,000 years, only about 300 occurred under water. Most of these eruptions happened in shallow water. Underwater lava develops through volcanic activity along the mid-oceanic ridges and plate boundaries, where the mid-oceanic ridges produce more lava than any continental eruptions. Such under water eruptions also harbour rich fauna unique to the vent area, such as red tube worms and giant clams. In the Pacific Ocean, there are ocean basins - volcanoes, of which there are estimated to be about 20,000 on the ocean bottoms of the world. Some of these form single mountains and others join with other volcanoes to form ridges. The highest volcanoes rise above the surface of the water as islands, which in many cases form linear groups such as in the Hawaiian Islands. Island groups are simply the highest summits of ridges. The submerged part of the Hawaiian Islands is among the largest and longest of these volcanic ridges - more than 1,500 miles (2,300 km) long. **************** Volcanoes in outer space Evidence of outer space volcanic activity has also been found. Space probes have detected the remnants of ancient eruptions on the Earth's moon, Mars, Olympus Mons and Mercury; these probably originated billions of years ago, since these bodies are no longer capable of volcanic activity. Triton (a satellite of Neptune), Io (a satellite of Jupiter) and Venus are the only bodies in the solar system besides Earth that are known to be volcanically active. The volcanic processes that occur in the outer portion of the solar system are very different from those in the inner part. Eruptions on Earth, Venus, Mercury and Mars throw out rocky material and are driven by internal heat. *** Mud volcanoes Mud volcanoes are a geological phenomenon that has largely escaped the attention of the public. Yet there are hundreds of thousands of them, scattered all over the globe. Over the past few decades, European scientists have been researching mud volcanoes in the bottom of the Mediterranean Sea. These come in different sizes, from knee high to as big as a mountain. They are often shaped like normal volcanoes, but instead of lava they expel a mixture of mud, rocks and gases. Most of the time they bubble away gently, but they can be dangerous. **************** Deep-sea creatures from sea floor volcano
Scientists from New Zealand and Japan recovered a variety of creatures while diving into the Brothers Volcano in the world's deepest-diving submersible research vessel named the Shinkai 6500. The 26-tonne vessel took a crew of three to the bottom of the ocean for eight hours, where they discovered numerous long-neck barnacles, shrimps, limpets, tubeworms, crabs and 'black smoker chimneys'. Reuters |
|
| News | Business | Features
| Editorial | Security
| Politics | Produced by Lake House |
Deep-sea creatures, some that may be new species, recovered from a
depth of 1,800 metres from the crater of a sea floor volcano northeast of
the Bay of Plenty are displayed in New Zealand.
