10 Awe-Inspiring National Park Nature Events

You don't have to take a hair-raising roller coaster ride for thrills or buy a pricey ticket to see beautiful plants in a botanical garden. You don't even need a trip to the zoo to watch amazing wildlife. Everything you're looking for — the excitement, beauty and fun — is waiting for you in America's national parks. Currently, there are 63 national parks and a total of 425 if you count National Seashores, National Historic sites and others. Read on for our picks of the most awe-inspiring nature events happening in national parks. Before you go, make sure the park is open and that you'll visit during the season or time of day that the event is likely to occur.

Sundogs might look like rainbows, but they're actually dense, colorful patches of sunlight that appear to the left or right, or on both sides, of the sun. While rainbows typically appear after a rain, sundogs like this one, at Alaska's Denali National Park and Preserve, may mean rain is on the way. They're formed when the sun is low in the sky and shines through a thin layer of ice crystals in the atmosphere. Like prisms, the crystals refract the light. When the moon shines through the crystals at night, these phenomena are called moondogs. Sundogs aren't visible every day, but they're not especially rare, either.

There are only a few places in the world — volcanoes, cracks or other openings — where molten rock breaks through the surface of the Earth and flows out as lava. Hawai'i Volcanoes National Park, on the Big Island of Hawai'i, is home to two of the most active volcanoes, Kīlauea and Mauna Loa. Eruptions release rocks, ash, lava and gases and can be deadly and destructive, but when no activity is expected, stop at the visitors center for information on trails and safety precautions. Then take Crater Rim Drive or Chain of Craters Road for incredible views of craters, lava tubes, cinder cones and more. Volcanic eruptions are fearsome but fascinating natural events, revealing clues about Earth's geology.

Alaska's official tourism site, Travel Alaska, predicts more Aurora Borealis, or Northern Lights activity, for the next two years. That's because sunspots, caused by changes in the sun's magnetic field, peak about every 11 years. The last peak was in 2014, so geophysicists expect more displays of the shimmering green, blue and violet lights to appear at high latitudes in 2024 and 2025. Glacier National Park in Montana is a great place to see them, thanks to its low light pollution and dark skies. Before you go, check the Aurora Forecast for recommended viewing times and locations. Other places to look for this spectacular nature event: Voyagers National Park in Minnesota and Theodore Roosevelt National Park in North Dakota.

When it's time to mate, certain species of fireflies flash in unison for a few days each year in Tennessee's Great Smoky Mountains National Park. Check the website to see when this annual nature event is expected again; it usually occurs in late May or early June in the Elkmont area of the park. Because this amazing light show is so popular, you'll have to apply through a lottery for a vehicle pass, and there is a fee. The bioluminescent beetles, also called lightning bugs, are one of only a few species in the world that synchronize their lights. If you're not chosen in the lottery, don't give up. There are other places to see synchronized fireflies in South Carolina's Congaree National Park. Learn more about them in acclaimed photographer Radim Schreiber's book, Firefly Experience.

Experience nature's power at Thunder Hole in Maine's Acadia National Park. You'll see and hear it at a tiny inlet with a small cave on rocky Mount Desert Island. When the water starts to rise before a high tide, or when storms barrel in, waves crash into the inlet and push the air out of the cave, creating a boom like thunder. For the best chance of hearing the boom, which doesn't always happen, head to Thunder Hole an hour or two before high tide. Check the weather before you go and prepare to get wet. Waves can reach 40 feet high here, and even in calm weather, waves can unexpectedly wash over the rocks.

The sight of hundreds of thousands of Brazilian free-tail bats, soaring out of Carlsbad Caverns National Park, is one of New Mexico's most awe-inspiring nature events. The bats fly out en masse to feed — sometimes as many as 200,000 to 500,000 at once — at sunset from April or May into October. Go back to the cave early to see them return before dawn. Individual bats fly back in from all directions, sometimes diving from hundreds of feet in the air and reaching speeds of 25 miles or more per hour. August and September are prime months for bat-watching if you want to see them fly with their babies. Park rangers give free bat talks, usually at the cavern entrance. Check the website to find out when the sun will rise and set and to verify the location of the talks.

The Chacoans, ancient ancestors of the Pueblo people, lived in an isolated canyon in what is now New Mexico's Chaco Culture National Historic Park. Known as skilled architects, they built various structures to track astronomical events for their ceremonies. One of the most impressive is Casa Rinconada. Every year, on the morning of the spring equinox — when day and night are roughly the same length — the sun rises over the canyon walls, beams through two of the casa's perfectly aligned doors and illuminates a small niche on the wall. The spring equinox is a traditional symbol of rebirth and renewal, and this natural event, framed so precisely, inspires many visitors. See the website calendar for ranger-led programs on the spring and autumn equinoxes, the summer and winter solstices and other topics.

Chunks of ice calve, or break off from glaciers, almost daily in Alaska's Kenai Fjords National Park in Kenai Peninsula Borough, about 130 miles from Seward, Alaska. Some visitors book day cruises to catch the spectacular sight when a glacier cracks and booms and splashes into the sea. More adventurous sorts paddleboard, kayak or camp around glacial lagoons, but rangers warn that getting close to a calving glacier can be dangerous. The largest known calving occurred in 2008 when filmmakers spotted a piece of ice as big as the tip of Manhattan split off. The warmer summer months are the best time to see the glaciers calve and watch icebergs — the broken pieces — bob in the waves.

Although no one has ever seen them move, the mysterious, moving rocks at Racetrack Playa, a dry lake bed in California's Death Valley National Park, have been studied for years. Also known as the "sailing stones," they tumble out of the surrounding mountains and move horizontally, leaving tracks — some up to 1,500 feet long — on the flat desert ground. Thanks to time-lapse photography, scientists theorize that a just-right combination of rain, ice and wind puts them in motion. This nature event starts when rain falls and freezes into a thin sheet of ice overnight. The next day, when the sheet thaws to just a few millimeters thick, the wind breaks it up into large panes. The panes float on a layer of water until they're blown against the rocks and push them along. The rocks have reportedly moved as fast as five to 15 feet per minute, for up to 15 minutes at a time. It's rare for all these conditions to line up; they occur only a few times each year. But the tracks are almost always visible.