Brandon McArdle's Postcards

Hey Mom, We just got to New Zealand and one of the first things that we did was to go to the Wai-o-Tapu geothermal area. It is a major geothermal area focused around Rotorua, in the north Island of New Zealand. One thing they showed us was a mud pool, and it was really cool. It is a geothermal phenomenon which occurs in geothermally active areas where there is a volcanic ash and sediment deposit. A magmatic heat source heats the ground water and causes it to rise to the surface. On the surface is a concentration of ash and other debris such as volcanic glass. The hot water mixes these deposits to create a substance called smectite, which is an expandable clay. An example of one type of smectite is called bentonite. Water causes it to expand because it is so polar. The water molecules build and stack on one another expanding the clay up to 10 or more times. This clay is very gooey and can even be used instead of soap. Looking onto the pool you may notice a bubbling which occurs in only certain areas. This is caused by heat which is able to break through of areas of least resistance creating a crack in the bedrock. This causes a continual escape for the heat and pressure which makes the bubbling effects. A mud pool is a much safer and less destructive release of the heat and pressure as opposed to that of a volcanic eruption because it is much more minor and constant. It also has a really bad sulfur smell which is from the release of hot magmatic air from below the surface of the earth. I know it doesn’t sound it described like this, but it is really cool. See you soon.

Love, Brandon

Hey, Mom. We made it to the South Island and we went to the Fox Glacier. It was really incredible. On our way back we saw a piece of ice left over from the glacier and the professors told us what is was. When a glacier recedes too quickly from getting too hot too fast, occasionally large pieces of ice will break off. Because they are no longer a part of the moving glacier it remains stationary. Over time glacial out wash and other debris cover that leftover piece of ice. Eventually, the ice melts completely, and when this happens the land created over the ice collapses to create a lake which is called a kettle lake. These lakes can be found all over the north east of the United States, like around where we live! Well, I’ll be home soon.

Love, Brandon