Sunday is a day off for most people in McMurdo. This Sunday, my field team went on a hike on the Castle Rock Loop Trail. There are several trails around McMurdo, with Castle Rock being one of the longest at almost 10 miles.
To do any of the longer hikes, you have to take a radio and check out
with Central Comms. You have to tell them what time you'll be back, and
make sure to check back in or tell them if you are delayed. Otherwise,
they will send the Search and Rescue team out to find you. This is
excellent in case of a real emergency, but not so excellent if you made
it back safe and just forgot to check back in, wasting bunch of people's
time and resources.
I found a link with a good map of the Ross Island trail system so you can see where we hiked.
We started near Building 155, went up around Twin Crater, and then got on the Castle Rock trail. We got off the trail where it ends and followed the Long Duration Balloon road near Scott Base and back up to McMurdo. On the map, there are a couple of emergency shelters marked -- these are called "apples" because they are small, red domes sticking out of the snow. The shelters have survival bags and first aid kits to help in case of an emergency, like if someone gets injured or bad weather comes in fast. Luckily, we only had to use them to eat lunch out of the wind.
 |
| This is the coolest picture I think I've taken so far. Erebus (left) with steam and Terror (right), overlooking the Ross Ice Shelf. Some of the sea ice has started to break up near the transition to land. Those tiny blobs near center-right are seals hanging out in the sun. |
We noticed a huge halo effect around the sun, which showed up in most of the pictures I took. This halo isn't an illusion from my camera; it's a real effect. Light from the sun is refracted by ice crystals suspended in the air. The sunlight goes into one side the hexagonal-prism shaped crystals, and is bent by an angle of 22° as it exits out another side. You can do the math to get 22° using Snell's law, and the index of refraction of ice. If you want to learn more details about the physics, check out this hyperphysics link (you can also click on "Calculation" at the bottom).
 |
| 22° halo with Mt Erebus. It's not a camera trick! |
This type of halo is often called the "22° degree Halo". There are other cool optical effects you can observe too, depending on the shape and orientation of the ice crystals, but the 22° is the most common. I'll keep my eyes out for any other types while I'm here!
Anyway, back from the physics tangent and more about the hike. We hiked next to Castle Rock, but couldn't actually hike up it. Later in the summer, they will install ropes to help people climb to the top. It's a rather precarious climb and people have been seriously injured while climbing it in the past, so I am perfectly fine waiting for the trail to the top to open up.
 |
| Castle Rock. So majestic and castle-shaped. |
I googled around and found a few papers that suggest that Castle Rock was formed subglacially (that is, under the ice). As the lava erupted to form Castle Rock, it melted the ice and cooled very quickly after coming in contact with it, forming a type of rock called hyaloclastite. Hyaloclastite is made up of glassy fragments in a fine-grained matrix.
Some geology explanation: The faster a rock cools, the smaller the grains are. The initial eruption of lava into the glacier formed glassy rocks, as they cooled extremely fast. As the next wave of fresh lava erupted, it broke apart the glassy rocks into shards, and cooled quickly as it came in contact with the cold water of just-melted glacier. This formed the fine-grained matrix that encases the glassy shards. A rock that consists of larger fragments inside a fine-grained matrix is also called a breccia.
If you would like another link to learn more about hyaloclastite.... here you go.
I guess I am feeling extra sciency today. Back to the hike. The hiking trail is marked by red/green flags along the route. Occasionally, there were black flags off to the side. Black flags mean DANGER and crossed black flags mean EXTRA DANGER. On the part of the hike down to the Ross Ice Shelf, there were a whole lot of crossed black flags, indicating crevasses. These crevasses formed along the slope down to the ice shelf, where the glacier is moving faster, causing the ice to stretch and crack. Many of the crevasses are covered with a layer of snow called a snow bridge, making them very difficult to see, and very easy to fall into if you aren't paying attention. Our team mountaineer took a break on the hike to tell us about crevasse safety -- if we do any field work in a crevassed region, we will be roped up, so if one team member falls in, they can be rescued by everyone else on the rope.
 |
| Red flags on the left mark the path up the hill. Black crossed flags along the ridge-line mark DANGER. |
PASSCAL has a test site out near Castle Rock that we passed by. We use this site to test systems and sensors in the cold, generally a season or two before we deploy those systems in an actual experiment (so we can make design modifications if needed). We are planning on taking a trip out to the test site in a few days to do maintenance and install some new sensors. Unfortunately, the solar panels were almost buried, so that means more digging for me.
Yesterday (day 7), my co-worker and I set up the equipment we are eventually planning to take out to Castle Rock in the warmth and safety of the loading dock outside our office.
 |
| Castle Rock test site equipment we are planning on installing this season. |
Here are some more pictures from the Castle Rock hike!
 |
| Me n Mt. Erebus, with a giant steam cloud. You can still see the 22° halo around the sun in the top left. |
 |
| Looking out at the shear margin next to the Ross Ice Shelf |
Here's a cool article about some science that was done on this shear margin in 2014.
 |
| Looking down a hill onto the Ross Ice Shelf. |
And finally, a picture of the heavy metal doors in the Crary science building to the outside. Not related to the hike at all, but I thought it might be interesting. Most buildings have heavy doors or a small room in between 2 layers of doors to keep the cold out.
 |
| The heavy metal door to the outside from the Crary science building. These doors are kind of hard to open. |
Alrighty, that's all for now!
Comments