Mail Buoy
September 20, 2001
Hi my name is Hannah, and I was wondering how long does it take the magma to harden after it is squeezed out?
Dear Hannah,
You might be surprised to learn that there are many answers to your question. It is important to understand that just like a lake freezing, a lava flow gets a solid crust fairly easily, but it takes a lot longer to freeze it all the way through. Thin pahoehoe flows get a hard crust in less than a minute after they stop flowing (experienced volcanologists can walk on them after just two minutes or so). Large a’a flows have a hard crust before they stop flowing (which is what makes their jagged surface).
For all lava flows, the time it takes for them to freeze totally is mostly a matter of their thickness. A one-foot thick flow takes maybe a half-hour to freeze. A flow 30 feet thick (typical of large a’a’ flows) can take months to freeze. The thickest lavas form what are called “lava lakes” (over 100 feet deep) and these can take years to freeze.
Thanks for following our expedition. Keep Diving and Discovering with us.
Regards,
Denny Geist
Hi, my name is Kevin Schuster. I attend the Clarke Middle school in Lexington Massachusetts and I am in Ms. Sheilds science class. When I read the September 15 update, I was wondering, how you can be sure that these eruptions occurred over 300,000 years ago? Before there was any recorded history!
Dear Kevin,
Another great question from Ms. Sheilds class! The 300,000 year age comes from a potassium-argon date of a rock from Alcedo volcano on Isabela. This date was obtained by Dennis Geist and colleagues from the caldera floor, where the oldest rocks are exposed. Elsewhere on the volcano they are buried by younger flows. The potassium-argon method relies on the fact that the natural decay of potassium-40 produces argon-40. Since the decay rate of potassium is known, and the amount of it in the rock can be measured, measurement of the argon-40 allows the age calculation. This is just one of the methods used to obtain ages, but it is one of the best for volcanic rocks. Older rocks have been found elsewhere in the Galápagos, but Fernandina and Isabela are the youngest volcanoes. The oldest rocks are found on the eastern end of the archipelago, with lava flows as old as almost 3 million years at San Cristobal and Espanola, so 300, 000 years is still fairly young.
We were just preparing a hot topic on how scientists determine the age of lava flows, so stay tuned for more information, it should be posted in a day or so.
Best wishes,
Mark Kurz
Dear Dan Fornari and/or Mr. Mark Kurtz
Hi, my name is Nico Timmermann. I live in Lexington, MA. My sience teacher, Ms. Sheild, told us to write a question to you so here is my question: I read that there were recent eruptions in the ocean, how recent was the last eruption and did it affect your work?
Dear Nico
Here in the Galápagos, there has never been an eruption in the ocean that has been witnessed. In two recent eruptions, at Fernandina in 1995 and Marchena in 1991, the lava entered the ocean after having erupted on land. Neither of these affected my work other than I wanted to stop what I was doing and go watch them.
On a worldwide basis, there are underwater eruptions all the time, probably several a year. Dan Fornari, one of our co-chief scientists, spends a lot of time searching for these lavas that are just a couple of years old. The most recent one I know of was at a place called Axial seamount, which is off the Washington coast a couple hundred miles. That eruption was a couple years ago.
Thanks for the great question and keep Diving and Discovering with us.
Regards,
Denny Geist
Hi
My name is Josh and I am in Mrs. Shield’s class at Clarke middle school in Lexington, Mass. The video footage that you have been sending back is really cool. I was wondering, how do you get close to the animals you photograph without scaring them off?
Hi Josh-
Many of the photos of the animals we’ve used in our web site were taken by the scientists and students during their travels around the Galápagos.
One of the unique things about these islands is that because they are protected, with visits by tourists to the different islands very closely controlled, the animals do not perceive humans as a threat, at least not like many animals do who live around cities or places with lots of people. Animals in the Galápagos. are rather tame when it comes to humans, although human impact on the islands has been quite severe in the past few hundred years.
Tourists who come to the Galápagos. generally come because they love to see nature in all it’s natural beauty and to photograph and watch the animals. Preserving the beauty of the Galápagos. and it’s animal and plant life is the work of the Charles Darwin Research Station and the Galapagos National Park.
Thanks for Diving and Discovering with us.
Best Regards,
Dan Fornari
I’m from Mrs. Shield’s seventh grade science class from Lexington, MA. On the Daily Update from September 16, you said that “Sea lions, penguins, marine iguanas and seabirds all depend on the cold Humboldt Current, witch delivers cold water plankton to the waters around the Galápagos.” So between January and May when the water is warm at the Galápagos, what do thoes animals do?
Thank you,
Mike Andryauskas
Dear Mike-
Thanks for asking a really interesting question. The warm waters that surround the Galápagos between January and May still contains plankton, but not as much as the colder currents between May and January. This is because the deep Humbolt current runs from Antartica up the Chilean coast and upwells to the surface at the Galápagos, bringing up lots of nutrients from the seafloor. The plankton then thrive on these nutrients and create large blooms that the fish feed on. The sea lions, penguins, iguanas and seabirds use this time when there are large numbers of fish and plankton, to buildup fat reserves in their bodies to see them between January and May when there is less food available.
It only becomes a major problem for these animals when the warm current lasts for much longer, such as during an El Niño. Because the animals are eating less, the fat reserves are being used up daily to keep them alive. Usually the reserves are large enough to see them through to May, but if the warm current lasts for longer, they can lose too much body weight and die. This is what happened when an El Niño occurred between 1997 and 1998, around 90% of the marine iguanas that lived on North Seymour died.
Thanks for Diving and Discovering with us, keep asking those great questions!
Sincerely,
Rhian Waller
Hi-
Its Angela from Ms Sheild’s science class. I was wondering how many volcanoes you found so far. If you know, about how often do they erupt per year?
Dear Angela,
We are studying the submarine flanks of the large volcanoes that have already been studied for many years by geologists above sea level. (Dennis Geist who is one of the co-chief scientists on the cruise has spent a good part of his career working on these impressive volcanoes.) We have discovered many smaller cones formed by eruptions on the flanks of the volcanoes, and we have found many unexpected features, such as the huge lava flows on the western flanks of Fernandina and Cerro Azul volcanoes. We don’t know how often these submarine eruptions take place because there have been so few submarine studies. We do know from the people who live in the Galapagos that one of the volcanoes erupts at least every few years. The last two eruptions were at Cerro Azul in 1998 and Fernandina in 1995 but there have been many others that were witnessed and documented by people, mostly in the western volcanoes (on Isabela and Fernandina).
Say hello to Ms. Sheild for us, and keep asking those good questions.
Mark and Dan
The following questions are from Julia to Karen Harpp.
Dear Julia,
It’s great to hear from you and to know that you have been joining us on the website for the past few days. My name’s Karen Harpp, and I’m one of the scientists on the cruise. I teach geology at Colgate University, in New York state. You’ve sent in some good questions, which I’m happy to answer for you.
Question number one: Why did you decide to become a scientist, and how did you end up going on Expedition 5?
Great question! I decided to become a scientist sometime in high school, I think it was around 9th grade. I had a wonderful geology teacher who took us outside around my hometown in Canada and showed us why the rocks and landforms looked the way they did. It made me realize how exciting it is to be able to explain the world around us...to understand why a mountain pops up in the middle of a flat landscape, or why a river makes big U-shaped turns. It was like solving a gigantic puzzle. So when I went to college, I studied both geology and chemistry, so that I could use both of those sciences to explain how the Earth works. It’s like being a detective; you get to solve mysteries everytime you look at something new in the world, like the volcanoes down here in the Galápagos.
I was lucky enough to be invited to participate on Expedition 5 by one of the chief scientists, Dennis Geist. He and I have worked together in the past on Galápagos volcanoes, and he thought I would be able to contribute some useful information to this new study. In my lab back at Colgate University, I have an instrument which allows me to determine the chemical content of rocks (a mass spectrometer). With the help of undergraduate students, we analyze the rocks and use that chemical information to tell us details about how the rocks were formed, which in turn provides another piece of the puzzle to help understand the Galápagos Islands.
Question number two: What’s it like to be on board, and what had been your favorite part?
It’s really exciting to be on board the RV Revelle as a participant in this expedition. We help with all aspects of the work, from processing rocks (which can get pretty grubby sometimes), to making sure the mapping systems are working, which we do by watching computer screen images in the lab. I have the 12-4 shift (with my watchmates “the Tiburones”...a great group of people who get pretty goofy sometimes), which means I work from 12-4 in the afternoon and in the middle of the night...Sometimes it gets pretty quiet on board during the latenight shift, but that is often the best time of day because you get to think more about what we’re doing here. When you’re out on the fantail and look across the completely black ocean, not a light to be seen other than the stars in the sky, it’s a pretty amazing feeling. First of all, you get a sense of how small you are compared to this planet, floating around on the enormous ocean. You also realize that the rocks we’re hauling to the surface are going to tell us secrets about how these amazing volcanoes have formed, more clues to the big mysteries. We also get an incredibly rare opportunity to see the ocean floor using the side-scan sonar, glimpses of the Earth’s surface that nobody has ever seen before! So I consider myself extremely lucky to get this opportunity to explore the Galápagos.
Question number three: What has been the most exciting day of your expedition?
I have to say that the most exciting few days for me was when we got to go north to Genovesa Island and collect ocean floor images and rocks from the ridge that extends northeast from that island. It was exciting to me because I spent 2 weeks on that island 2 years ago with some Colgate students, mapping the island and trying to understand its history. We suspected there was a big ridge that might be volcanic nearby, meaning the area might be much more volcanically active than previously believed, but we had no proof. Using the mapping system on board the Revelle, we got to collect detailed images of the ridge, and prove that it was definitely volcanic. I realize this may not sound that exciting unless you’re working on this project yourself, but to have this chance to see an area which you could only guess about before and which you thought you’d never get to see was absolutely incredible.
I hope this answers your questions, Julia. If you have any more, just send me email!
Take care, and good luck.
--Karen
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