Introducing Mountain Building & Volcanism (Volcanoes!)
Mountains have always fascinated people, and we are especially fascinated when those mountains erupt, hurling melted rock through the air and endangering our lives. In Module 3, we will explore more about how mountains are built, and about volcanoes. We will start with a little history of humans and volcanoes, mostly for fun—you do not need to memorize how the legend of Atlantis is related to volcanoes, but you may be interested. Then, we will get into the important material, starting with what to do for Module 3 followed by the Module 3 Main Topics.
If you’re lucky to visit Italy, you may be able to stop at Pompeii and Herculaneum. These cities were buried, more-or-less intact, almost 2000 years ago (in the year C.E. 79) by a great eruption of the volcano Vesuvius. Most of the residents escaped when the volcano first became active, but well over 1000 people remained and were killed by the major eruption, mostly by the heat of glowing flows of gas and volcanic ash (called pyroclastic flows), which were roughly 250oC (480oF) at Pompeii. The ash that buried the cities piled up roughly 5 m (16 feet) thick. The Admiral Pliny the Elder was trying to rescue people and died in the eruption. His nephew Pliny the Younger, who was farther away and survived, left the following account:
They tied pillows on top of their heads as protection against the shower of rock. It was daylight now elsewhere in the world, but there the darkness was darker and thicker than any night…(t)hen came a smell of sulfur, announcing the flames, and the flames themselves…he stood up, and immediately collapsed…his breathing was obstructed by the dust-laden air.
--Pliny the Younger
Many other volcanic eruptions have affected human history. And, the legend of Atlantis may involve a volcano. Supposedly, Atlantis was an island civilization "outside the Pillars of Hercules" and thus located in the Atlantic Ocean, where it was destroyed by an earthquake or tsunami (giant wave) about 11,000 years ago. The source of this information (according to Wikipedia and many other sources) is an account that Plato wrote in 360 BCE of information reportedly given to Solon two hundred years earlier by priests he visited in Egypt. Now, if someone told you that 200 years ago someone else had received information from yet another person regarding something that happened 9000 years earlier, would you immediately believe it? A lot of people apparently do; a search of Google for "Atlantis Plato" finds about 4.8 million matches, and not all of them are academic discussions.
A better question might be whether there really are islands that disappear below the sea. The answer is yes; many do. Some slide slowly downhill, at about the same rate as your fingernails grow, and disappear first beneath the waves and finally beneath the continents. Others suddenly explode, scattering themselves across the world. The Atlantis story actually may come from one such explosive volcanic eruption in the 1600s B.C.E. that destroyed most of an island at what is now Santorini in the Mediterranean Sea, and pushed a giant wave (tsunami) perhaps 300 feet (100 m), or more, high across the coast of Crete, probably contributing to the eventual demise of the Minoan civilization there.
Before we go any further, take a look at the following short video introduction by Dr. Anandakrishnan...
Video: Master of the Lamp (3:02)
Sridhar Anandakrishnan, Geophysicist and Glaciologist: Hey, groovy cats. Welcome to my pad. This is the GEOSC 10 '70s show, in which we're going to talk about vinyl, bell-bottoms, platform boots, and most importantly, lava lamps. What? You mean you don't have a lava lamp? Run down to Uncle Eli's right now and get one. I'll wait. So what do lava lamps and GEOSC 10 have to do with each other? Well, they're a wonderful analog for this whole first section of GEOSC 10. The first section, if you remember from looking at the syllabus, is building mountains. And the short story for building mountains is heat from within the Earth. We're going to talk about tearing down mountains later on, but right now we're talking about building mountains, and the heat within the Earth is what drives that whole process. And a lava lamp is a beautiful example of that. Let's take a look at it. What we have here is a glass tube with some water in it, and then these globules of a slightly different material, and at the bottom we just have a light bulb that produces heat and heats up the bottom of this glass bowl. All right, I'm going to take this apart here, and just take a look on the inside. I don't know if this is going to be too bright for you, but we have a light bulb underneath here, and its only purpose is to produce heat and to light up this glass bulb a little bit. These green globules in here get heated up at the bottom, and as they get heated up, they get less dense. This is fundamentally what's happening inside the Earth. Rocks get heated up at depth because there's a lot of heat trapped inside the Earth. As they get heated up, they get less dense, and just like these lava lamp globules, they rise up like this one's doing right now, up to the surface of the Earth. When they get to the surface they cool off, and then just like this one, they sink back down into the Earth and the whole process goes on and on again. This inside the Earth we would call a convection cell. In a lava lamp, we call it cool.
Learning Objectives
- Explain how the creation of sea floor at spreading ridges is balanced by the destruction of the seafloor at subduction zones.
- Explain the different types of volcanoes that form at spreading ridges, subduction zones, and hot spots.
- Identify the different types of hazards caused by volcanoes and the increasing but imperfect ability to predict eruptions.
What to do for Module 3?
You will have one week to complete Module 3. See the course calendar in Canvas for specific due dates.
- Take the RockOn #3 Quiz
- Take the StudentsSpeak #3 Survey
- Submit Exercise #1
- Begin working on Exercise #2
Questions?
If you have any questions, send an email via Canvas, to ALL the Teachers and TAs. To do this, add each teacher individually in the “To” line of your email. By adding all the teachers, the TAs will be included. Failure to email ALL the teachers may result in a delayed or missed response. For detailed directions on how to do this, see How to send an email in GEOSC 10 in the Important Information module.
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