More than 2.5 million people visit the volcano annually, which is located inside Hawaii Volcanoes National Park. The park contains more than 150 miles of trails for walking and hiking. Biking is allowed on roads and some trails and there are campgrounds inside the park.
"I used to go before dawn and watch the sun rise over the lava flows," says Williams. "It was just stunning." The park is open 24 hours a day, so nighttime viewing of the glowing lava is also a possibility. Viewing conditions are variable, so research the best viewing spots and safety advisories online.
Kilauea in Hawaiian means "spewing" or "much spreading," and is the youngest of the Big Island's volcanoes, according to the U.S. Geological Survey. It is believed to be the home of Hawaiian volcano deity Pele.
Eldfell, Vestmannaeyjar, Heimaey, Iceland
Elevation: 915 feet
Eldfell, Icelandic for "mountain of fire," was believed extinct when it suddenly erupted in 1973, forcing the evacuation of the entire population of the island Heimaey, which is among the Westman Islands. The volcano has been inactive since the eruption.
Most of the town of Vestmannaeyjar and its harbor were saved from the lava flow by using large pumps to spray seawater onto the lava, cooling it enough to stop its movement.
"That was maybe the only case that man has had any ability to successfully affect a lava flow," says Williams. "It was only because they had an unlimited amount of water."
In addition to tours of Eldfell and Helgafell volcanoes, Vestmannaeyjar features a thriving fishing industry, whale watching expeditions and a museum of natural history.
Mount Erebus, Ross Island, Antarctica
Elevation: 12,444 feet
Mount Erebus, the second tallest volcano in Antarctica and the most active Southerly volcano in the world, is home to an active lava lake that sends puffs of steam into sub-frigid air.
"When the lava cools and a crust forms, it (the crust) will move and then sink down again," says Williams.
Under the cover of total darkness for four months of the year, the only way to reach its summit is by helicopter or walking in temperatures ranging from 4 to 60 degrees below zero. Definitely not the most hospitable volcano on the list, but Williams says she dreams of doing research there because it combines her two favorite things: volcanoes and Antarctica.