Scientists believe the hole left after the explosion filled up with snowmelt and rainwater over the next 600 to 800 years to form Crater Lake. Because the volcanic terrain limits the amount of nutrients in the lake and bars streams from coming in or out of the lake, the water is pure blue and largely comprised of snowmelt.
The lake is a U.S. National Park.
The last time the lake froze over was in 1949.
About a half a million tourists visit Crater Lake every year and the most common question among them is, "Are there fish in the lake?" Yes, according to park rangers.
William Gladstone Steel, an explorer who helped establish the lake as a national park, carried buckets of minnows into the lake after his first visit in 1885.
Only two species of fish--kokanee salmon and rainbow trout--out of more than 40 introduced to the lake have survived, however, and the populations are sparse. The public is allowed to fish in the lake without a license.
The lake is as about six miles wide. And its water typically stays at a constant level, given the annual snowmelt and rainfall is roughly equal to the lake's evaporation and seepage.
Another common species of Crater Lake is the olden-mantled ground squirrel, a tiny brown animal that can be spotted foraging all over the park.
Collier and others are collecting samples of moss beds in the lake in order to study its age and the overall ecosystem of Crater Lake.
In the future, Collier hopes to be able to conduct field studies and watch biological changes in the lake from fiber-optic cable hooked up to video cameras and sensors installed in the water. "But it will be hard to get cables down there," he said.
Scientific experiments have been conducted on Crater Lake for the last 100 years. But in 1994, the National Park Service established a program to continuously monitor the park indefinitely. The lake is pristine, except for the introduced fish species.
A model of Crater Lake at the Sinnott Memorial Overlook gives visitors a broader prospective of the lake's clarity, depth and structure.
Unlike Lake Tahoe, which at a depth of 1,700 feet rivals that of Crater Lake's 1,932 feet, the park is largely unpopulated and un-commercialized. The lone lodge at the rim, called the Crater Lake Lodge, is nearly 100 years old and has only 71 rooms. The historic lodge was redone 10 years ago, so it's now as pristine as the lake, but prospective tourists often have to reserve a room years in advance, or camp down the mountain.
"We're talking about hundreds of thousands of years of geology exposed," Collier said.
An engineer on the research boat controls the remotely operated vehicle, or ROV, at a depth of 450 feet in the Danger Bay area of Crater Lake. He can watch the robot and its surroundings from a video signal transmitted to the PC-to-television hookup.
Sonar on the top of the robot also collects data on the biomass of the moss, blue-green algae and other life in the lake.
The robot has seven thrusters--four mechanisms to go forward and back, two to go side to side, and one to spin. It is also neutrally buoyant, meaning that it doesn't sink or float. It's controlled by a so-called altimeter, which measures depth and can be set to stay a certain distance from the lake floor or caldera wall.
Two engineers on a boat control the robot's movements. Data and video from the robot is transmitted via wire to a computer on the deck of the boat. The PC takes in and transmits signals from the altimeter.
A tree covered in moss on the only trail leading to the lake. The walk down is a cinch compared with the climb up, which can be compared to walking 150 flights of stairs to the 75th floor of a building.