We’ve been to see a huge glacier. It’s so big and famous it’s even got its own name – it’s called the Perito Merino Glacier. It’s in Argentina, close to the border with Chile. And it’s famous because every day it is possible to get really close and watch pieces of the glacier break off and fall into the lake. The word used to describe the pieces of ice falling off is “calving”. Have you heard that word before? It’s also used in farming to describe some animals giving birth.
The glacier is really really big. The front where the bits break off is about 60 to 70 metres above the water of the lake. That’s more than twice the height of an ordinary house. And the ice is about three times as deep below the water.
The ice forms high up in the Andes mountains. There is so much of it that it is force very slowly down the mountains towards the river. You can’t see the movement with your eyes because it is growing and moving so slowly – only a few millimetres a year.
When we stood in front of the glacier we heard lots of loud noises – cracks and bangs. These were caused by the movements in the ice. This is the sign that the ice is breaking up slightly and pieces will break off soon. Sometimes the ice falls from the very top and lands in the water with a loud crash and a big splash. Sometimes the ice falls off from lower down and makes less noise because it doesn’t have to fall so far. Sometimes the ice breaks off from underneath the water. Then it floats to the surface with lots of noise and rushing of water. We saw one very big piece of ice suddenly appear from under the water in front of the glacier. It rolled over right in front of us, just like a huge whale rolling in the water. We could see the bright blue and white colours of the ice, but this block of ice also had mud stuck in it from the bottom of the water and we could see that too.
Once the ice has broken off the glacier it begins to float away and then starts to very slowly melt as it sits in the water. Eventually these pieces of ice disappear completely and become water again.