英語(yǔ)聽(tīng)力：自然百科 夏威夷火山（下）

Although the big island reveals the most dramatic displays of volcanic power, every one of the Hawaiian Islands bears witness to a fiery past. The Hawaiian chain stretches for more than 1,500 miles through the heart of the Pacific, the most isolated archipelago on earth. In the southwest, lie six main islands and two smaller ones. Their rugged landscapes provide clues to the forces that shaped them.

Time and tide, wind, water and fire -- they have sculpted Hawaii over millions of years. Jagged cliffs, the remnants of extinct volcanoes, rise 1,000 feet above the sea, they testify to the combined power of erosion and seismic forces. Magnificent canyons were created when earthquakes twisted and split the landscape.

Giant craters are evidence of past eruptions, and hint at new ones to come. The most ancient volcanoes, worn down by the elements, now lie hidden beneath a carpet of green.

One of Hawaii's most famous landmarks, Diamond Head, looms above the beaches of Waikiki. The sight is postcard-perfect, but few realize that 10,000 years ago, this, too, was the scene of a violent eruption as lava fountained from these walls and spilled into the sea. Today, nearly half a million people live in the shadow.

Hawaii's volcanoes did more than sculpt the landscape. They actually built the islands from scratch. The Hawaiian chain sits atop of the Pacific plate, a shifting block of the earth crust. Beneath the plate lies a stationary hot spot. It produces a column of magma, creating volcanoes that gradually rise above the sea to form islands. As the plate slowly drifts northwest, each island in turn is pulled away from the hot spot, and the volcanoes are extinguished. The hot spot now sits 20 miles south of the big island, where it's creating a new volcano named Loihi. To see it, you have to head underwater.

Keeping an eye on the young volcano, scientists like Terry Kirby, journey down in a manned submersible.

"We've (n)ever known where we're gonna find it for nearly a year. And this year there was a little more anticipation, because we heard that there was some seismic activity."

The slow descent to Loihi takes hours through waters that grow darker and colder. Though the mountain has grown two miles above the sea floor, its summit is 3,000 feet beneath the ocean surface. Inside a newly formed crater, the tiny submersible is dwarfed by Loihi.

Like any active volcano, Loihi is inherently unstable. Seismic tremors in the interior can trigger landslides.

"I definitely am aware of what can happen down there. We see these gigantic boulders down there and we have the... We wouldn’t wanna be down there when one of those things came down. So, we are always really tuned in to any kind of sounds, any kind of vibrations. "

A few species have adapted to this hostile environment, managing a precarious existence. Beneath the rugged terrain, the same inferno that feeds Kilauea is constantly reshaping Loihi. Delicate pencil chimneys rise from surfaces strewed with rubble. Frequent earthquakes cause old structures to crumble，while new ones form.

"It's pretty amazing. This is actually part of the wall that collapsed two years ago. We see the edge of it, coming up here, very sharp ridge that used to extend quite away, further out . And all that caved in and came down a couple of years ago."

As part of their routine survey, they will check the volcano's temperature. Vents in Loihi's flanks release blazing heat and dissolved gases. The number steadily climbed to well over 150 degrees Fahrenheit.

"That's amazing. I think (that) the ambient water is almost freezing, and there is weird water flowing out of this almost ice-cold water. That's 200 degrees Fahrenheit."

Scientists will continue to monitor the young volcano. More earthquakes and collapses areinevitable.