Here are some important to know about landslides
The largest subaerial (on land) landslide in Earth's recorded history was connected with the 1980 eruption of Mount St. Helens volcano in Washington state, USA. That landslide had a volume of 2.8 cubic kilometers of material and the landslide traveled about 22.5 kilometers down the North Fork Toutle River. The landslide depth was 150 feet with a maximum depth of 600 feet. The landslide velocity was somewhere between 70 and 150 miles per hour.
Palu, a city in Indonesia, had a tsunami, and an earthquake, and debatably, that all started with an underwater landslide. The underwater landslide was very big for a landslide and ended up causing huge devastation on the surrounding areas.