When a lot of snow falls quickly down a mountainside, we call it an avalanche.
The roads north of Aspen were closed for several days due to the avalanche. So much snow had fallen on them that no cars or trucks could pass through.
Mountain¬climbing or skiing on the mountains on your own can be very dangerous. Weather conditions, mild earthquakes and even loud noises can cause snow from the tops of the mountains to fall over and cause a massive avalanche that can bury you in snow.
Avalanche does not just mean a large amount of snow falling. We use it figuratively for any large amount of something, especially when it surprises us. In this sense, we usually say there is an avalanche of something.
After the professor made some controversial comments on facebook, there was an avalanche of criticism on social media and in the campus press. She was forced to resign from all the bad publicity.
An ice floe is a large, mostly flat piece of ice that is floating on water. It is usually found on rivers, lakes or oceans.
Sean looked through the binoculars and saw a penguin floating on an ice floe. The piece of ice must have broken off and made a natural raft for the bird.
The river was blocked up by an ice dam and even starting to flood. A couple of ice floes were stuck in the rocks and blocking the flow of water.
An ice floe is relatively small or flat, but an iceberg is a large chunk of freshwater ice that has broken off a glacier and is floating in the ocean. Often, the part of the iceberg that is visible above the water is just the tip of a much larger piece underwater. When something is just a small part of a much bigger problem or task, we often say it's just the tip of the iceberg.
Icebergs can be quite dangerous for ships near the Arctic and Antarctic regions, where there is a lot of ice. In fact, the famous Titanic sunk when it hit an iceberg in the North Atlantic.
Sally said that she has a big project to work on, and that's just the tip of the iceberg. After this project is finished, she has to prepare a Powerpoint presentation to explain the project to her manager.