iceblog!

Back Out: Ice Towers

The day after Christmas dawned warm. The day after Christmas dawned really warm. I was ready to have my picture taken outside in a t-shirt. I would have been just for show, but still, that thought doesn't occur to me normally. Bill and Rich Esser headed off in the helo to work on a site on the other side of the volcano, Rich K. headed off in a helo to McMurdo to do some work down there, and Nelia and I headed into the backyard to survey ice towers.

The ice tower task is fun, on a nice day. The work consists of poking around different ice towers, recording some information about each. The ice towers are formed where heat comes up through the ground, causing moisture in the air to precipitate. Many of the towers have caves underneath. The caves have rock floors and ice ceilings. Caves, Nelia thinks, are formed when warm rock melts the snow floor above it. If this doesn't make sense, let me know. The ice towers are commonly in lines, or likely along fissures--cracks in the ground. The cracks can be quite small--not like the huge breaks in the Earth I imagined as a kid when I thought I could get swallowed up during an earthquake. I'm counting on your imagination being similar, otherwise you have no idea what I'm talking about. Anyway, the basic idea is: Volcano. Hot components. Hot components like magma chambers within the volcano and cooling lava flows at the surface. The heat from magma bodies can leak out through the overlying rock, as can gases which are expelled from the magma as it rises and cools. The ice towers on Erebus form around fumaroles, which are vents of heat and gas on a volcano. We measure CO2 output at the fumaroles/ice towers to see if the gas forming the ice tower is magmatic, and to see if the CO2 output varies from year to year. This can help us make guesses about what is happening within the volcano.

Plus, it's fun. My explanation of why the ice towers are there and why we're studying them is botcher, because 1) it's outside my realm of 'expertise,' and 2) it's late, and I'm writing off the top of my head. Then again, I always do when blogging. If you have more questions about the ice towers, let me know. If I can't explain, I can ask someone who can, and then I can use their words.

But you can see as well as I can that the ice towers and ice caves are pretty neat. Here's a photo shoot of Dr. Nelia Dunbar with ice.

The ice towers in our backyard.

Nelia knocks away fragile snow near the entry to get a better angle for making measurements. We probe the way up to each ice tower to see if it's safe; the snow near ice towers is liable to be thin, and can fail under the weight of the likes of us.

In both photos, Nelia measures wind speed coming out of entrances. We also measured CO2, estimated the size of the entrance, and took a GPS reading of the approximate location of the tower, using handheld GPS.

Concentric bands of blue ice near a tower give some clues about tower formation. Nelia thinks the ice represents an old tower, that has since migrated to the current location.

Now for the gratuitous part: Nelia and I enter at the base of another tower, which guards the entrance to a decent-sized cave.

Nelia says the cave is usually bare rock, with a dripping ice ceiling. Now, after the recent wind and snow storm, the front rooms and passageways are drifted with snow.

Thin cave walls letting light through.

Snow lace on the walls.

Nelia jots some notes in her field book.

Ice jail bars, about 4 inches high.

Ice penguins, probably about one foot high.

Close-up of an ice wall. Crystals are probably about 1 cm across.

Time to exit.

Pretty amazing to come up and realize what you've just been clamboring around under.

And that was only the first half of the day. Tune in next time, when I tell you about something else.

Posted by beth at December 26, 2002 10:08 PM | TrackBack