There are two types of glaciers, continental and alpine. For the most part, we have studied Alpine glaciers in the last two labs. They are also known as valley glaciers, and as you know are found on mountain tops above the snow line. The accumulation zone begins in a bowl-shaped cirque, eventually it spills outs and flows downwards. Alpine glaciers are found on every continent, but Australia.
WBLT Geoscience Students on Corona vacation: This will cover Semester 2, Class 10. Complete the lab sheets which can be added to your Geoscience binders.
In this post, All Things Ice, we will check out continental glaciers, Greenland specifically, and learn more about land and sea ice. Our labs will involve playing with ice and water, and will cover saltwater density, iceberg science, and water displacement.
Make Ice for Labs
Dark colored ice cubes will need to be frozen ahead of time. You can use an ice cube tray. We used medicine cups, but personally, I think the ice cube tray works best…
- Mix a 7-8 drops of liquid dye into a glass of water and stir.
- Then fill an ice cube tray or medicine cups and freeze overnight.
- Darker dye colors work best, as yellow will be difficult to see.
Supplies for all labs:
- Two large clear cups or jars
- Two raw eggs
- Liquid Dye
- Salt
- Tap Water
- Stirring Spoon
- Pre-frozen colored ice cubes
- Black marker mark water line.
- Colored pencil that matches ice cubes
- Pencil
Printable Lab sheet
Like all scientists, we need some information about icefields and ice sheets before we can apply the lab information to real life.
Icefields
Besides the Alpine Glacier, the second type is a Continental Glacier which comes in two sizes: icefield (small) and ice sheet (large). Icefields are a lot of glaciers connected together with only Nunataks, (mountain peaks) exposed. Isn’t that a cool word? Nunatak?
Ice Sheets
Ice sheets are found near the poles where elevation doesn’t matter because it is always cold above the arctic circle. There are two ice sheets on earth: Greenland and Antarctica. Greenland, the world’s largest island, is the smaller of the two ice sheets. Eighty percent of the whole island is covered in an ice sheet. Only some of the coast line of Greenland is free of ice.
Not-so-Green-Greenland
The photo of Greenland is rather white, isn’t it? Let me sidetrack for just a moment.
When the Vikings settled in Iceland, they named it after floating icebergs found in the area. Erik the Red, a Viking with a really bad temper, was exiled from Iceland, for three years, for being found guilty of murder. He was already exiled from Norway, his native country, so returning to his homeland wasn’t an option. Red-haired Erik (thus his name) did a lot of exploring and finally settled on a large island to the west. To entice others to settle with him, he called it Greenland.
Eyeeee don’t know about you, but I think the other settlers knew rather quickly that they got sucked into a large continental-ice-sheet-sized lie! Lying is not the way to get people to follow you!
The continental glacier of not-so-green-Greenland is the largest ice sheet in the North Hemisphere. It also calves gigantic icebergs – about 15,000 a year! Take a look at the continental glacier in Greenland in the following video. If you have done the previous labs and videos: Study of Glacier Movement and Anatomy of a Glacier, you will notice right away that continental glaciers look very different!
Pack Ice and Icebergs
Greenland has two types of icebergs: pack ice and of course, icebergs.
Pack ice begins and ends in the ocean. It is similar to ice on a frozen lake, except pack ice is frozen salt water in the arctic. This type of ice is seasonal, meaning most of it freezes in the winter and melts in the summer.
Glaciers, calve icebergs which float away. Ice sheets give birth to really, REALLY large icebergs, like the one below!
There’s one thing we need to do before starting student labs, we need to cover the term density.
Density
To understand density, you have to know two things about an object: volume and mass. Volume is how much space an object takes up and mass is what it is made of, or how heavy it is.
Look at mamma cat and kitten. Which one takes up more volume (space)? Which one has more mass (weight)? Momma does, on both accounts.
Here is another example. If I have a jar of marbles and a jar of cotton balls, I think we will agree that the volume of both objects are the same size, and that they both take up the same amount of space. But what about mass?
The object that is heavier has more mass. Marbles are much heavier than cotton balls therefore the marble jar has a higher density.
The science labs will help you understand the density of water.
Begin All Things Ice Student Labs
Stop here, and begin your labs. There are four ice labs, and they all operate off the same two glasses of fresh water and saltwater.
When you are finished with your labs, come back to this section.
After Lab Completion
Salt Water Density
Icebergs are large masses of heavy ice and yet they float. Like the egg in saltwater (Lab 1), icebergs might be heavy but the dense water holds them up, so they look cool, bob about, and attract a lot of gawking tourists!
Saltwater is dense therefore icebergs float – just like the egg!
Iceberg Density
Icebergs can be massive. (Notice the word ‘mass’ in massive.) To understand icebergs, we need to understand their density. This large floating mass of ice is heavy and sits low (Lab 2) in the water. They are dangerous because the larger, underside can’t be seen.
Icebergs can also change shape by melting or by calving off pieces of ice. When the center of gravity changes, an iceberg can flip and roll causing tsunamis and even, earthquakes.
The following video is a photo of an iceberg flipping over. You can see why getting to close to an iceberg can be as dangerous as getting to close to a glacier.
Convection Currents
When the ice cubes in Lab 2, Part B, started melting, the temperatures in the freshwater glass created a lot of movement. Cold is dense so it sinks. Warm is less dense and it rises. It doesn’t matter if we are discussing air or water temperature, because both will react the same way. The rise and fall of warm and cold are called convection currents. Because of this, the fresh water was continuously moving.
Just like lab 2, Part B, polar ice creates the convection currents that drives the motion of all the oceans on earth!
While the freshwater glass had all the action, the saltwater was so dense it didn’t allow much movement. The density kept the colored melt water at the top of the water line.
However, melting glaciers and icebergs release fresh water into the ocean making it less salty. This changes the density of the water and creates ocean currents. If we had added more ice into the saltwater, the water would have become less salty (less dense), and you would have seen more currents.
Water Displacement
It is summer time, you are on a diving board and you do a beautiful, belly flopper right into the water. Aside from the fact that it hurts, (poor you) what happened when you entered the water? Your body mass pushed the water out of the way! It had no choice but to make room for you.
The same thing happened when you added the ice cube to the water – (Lab 3), it displaced the water to make room for its own mass. But, when the ice cube melted, it didn’t make the water table rise, it just filled in the original space that it took up. This is called ‘water displacement’.
When the faucet added water to the glass (Lab 4), the water rose above the marked water level. The same happens when a glacier, river, or general runoff is added to the ocean, the water table rises.
Iceberg colors
Were you amazed at the color of the rolling iceberg in the video above? Icebergs come in a variety of colors and shapes as you will see in the next Geoscience post. Below, check out the world’s largest iceberg! It was born in the year 2000, from the continental glacier that covers Antarctica.
All Things Iceberg
Most humans think of icebergs as a danger that sinks ships. But in reality icebergs bring land-nutrients to ocean life as they melt. As we saw in the labs, icebergs also create convection currents that puts all of the earth’s oceans in motion! The circular currents stirs up food from the ocean’s bottom and then circulates it feeding the marine life that live near the top zones of the ocean. Glaciers and icebergs play an important role in earth science!
Share your thoughts and lab results with us!
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