Landslide. Mudslide. Rockslide. Debris Flow. Avalanche. Lahar.

These all pretty much mean that something is moving downhill. And it's often due to heavy rain, melting snow or the movement of some other type of sludge.

"Landslide" is the all-encompassing term for the rest of the events, and it simply means that some piece of earth is moving downslope.

Here are 10 things to know about all types of landslides: 

1. Anything that can move can be part of a slide or flow. You’re probably used to hearing about rockslides or mudslides, but did you know that lava can flow with water? What about chunks of forests going downriver? Both of these have happened.
2. There are two main types of mudslides. The first type is a mudflow, which is just the movement of water and mud. This type is usually shallower — about 15 feet deep or less. The second type is a debris flow. This is when water brings down mud and other debris like rocks, branches and even large boulders.

3. Mudslides can move as fast as 35 mph, and they often get faster as they move downhill. As the soil and mud slides, it accelerates downhill, gaining momentum. This fast motion of mud, trees, rocks, water and other debris can sound like a freight train as it nears your location. 
4. Landslides kill 25 to 50 people every year, on average, in the United States, according to the USGS. Thousands die in rock falls, debris flows or volcanic slides every year around the world.
5. Debris flows can occur under blue skies. Multiple debris flows can start at different points high in canyons, then funnel into channels, merging and gaining volume, which allows them to travel a long distance from the source. The places most at risk for mudslides are at canyon bottoms, stream channels, outlets of canyons and slopes excavated for buildings. If you live in those areas, be on the lookout for immediate signs of a pending mudslide, including tilting trees or sudden changes in rivers, especially after rain.
6. Wildfires can make mudslides much worse. Vegetation helps anchor soil in place on hills, even during heavy storms. However, when this protective vegetation is burned off, hillsides become vulnerable to erosion and the slopes can come crashing down during mudslides. Heat, ash and oily residue from wildfires also make it harder for water to infiltrate the top layer of soil, making the ground almost water-repellent. The elevated risk of debris flows in a burn scar can last up to five years after a fire.
7. Landslides can cause tsunamis. Rapidly moving volcanic or glacial landslides have been known to displace massive amounts of water in the Pacific and Atlantic. In 1958, a 7.9 magnitude earthquake triggered a rockfall that created a nearly 100-foot-high wave in Lituya Bay, Alaska. 
8. Major rainfall and snowfall events are the largest source of landslides. Any time land is weakened by a weight from above, it is increasingly likely to flow or fall with gravity. Melting snowfall can unleash slides months after the snow fell and thousands of feet lower in elevation.
9. Your insurance may not cover landslides. Many places consider landslides as a flooding event, which they are, but this puts the damage that they cause under flooding vs homeowners’ insurance. In some spots, slides could be covered by earthquake insurance or by a difference-in-conditions policy. The best approach here is to reach out to your insurance agent and ask what your policy actually covers before an event occurs. 
10. Lahars are one of the fastest-moving landslides, and they can be due to volcanic eruptions. In steep terrain, this slurry of hot or cold water, rock, ice, cooled lava and vegetation can travel at more than 120 mph. This mixture can come through like a wrecking ball, passing through areas of least resistance. They will carry away or bury any objects in their way, including cars, agricultural land or buildings. 

Jonathan Belles has been a digital meteorologist for weather.com for 10 years. His favorite weather is tropical weather, but also enjoys covering high-impact weather and news stories and winter storms. He's a two-time graduate of Florida State University and a proud graduate of St. Petersburg College.

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