By Arnie Cerny
Have you ever heard of the lost continent of Atlantis? Where was the lost continent of Atlantis? Historians have speculated that it was in the middle of the Atlantic Ocean, off of the coasts of both Spain and France, and also in the western Mediterranean Sea. We do not know for sure where it was, but in 1956 a Greek seismologist by the name of Angelos Galanopoulos suggested that the great continent was located in the eastern Mediterranean Sea. More specifically south of Greece on the island of Santorini, which was called Thera in 1470 B.C. He believed a great volcanic eruption was the end to this wonderful civilization.
Plato, a great Greek poet and historian, was fascinated with an ancient Egyptian story of a fantastic civilization which was lost during a terrible catastrophe. Plato called this civilization Atlantis. He depicted Atlantis as the greatest civilization of its time. The people were famous for their beauty and their culture. Plato wrote about this beautiful place one thousand years after it was destroyed. His writings were based on ancient Egyptian writings and his translation of the language was questionable.
Plato made a mistake in his math!!! He claimed the lost continent to be about ten times the size that it actually was. He also put the time of the calamity to be about 9000 years before the rise of the great Athenian empire, which was about 10 times earlier than it could have really occurred. Historians now believe that Atlantis was destroyed about 900 years before Athens. A factor of ten was the problem with Plato's accounts, ten times too large and ten times too early.
What happened to wipe this superior civilization off the face of the Earth? A great volcanic eruption was the cause. A volcano named Santorini exploded with such fury that it not only blew most of the island into the heavens but also caused a huge tsunami that wiped out many of the neighboring civilizations.
When Santorini erupted, much of the volcanic cone exploded into the atmosphere and over 32 square miles of the island was destroyed. What happened next was the formation of a caldera. A caldera is a bowl shaped depression caused by the magma chamber under the volcano emptying during an eruption and the volcano falling into the magma chamber because of its own weight. When the caldera formed, a series of tsunamis produced by the crashing of the top of the volcano wiped out many cities and towns in the eastern Mediterranean. This tsunami was reported to have reached the height of over 300 feet. The explosion was heard as far away as Sweden, and the earthquakes produced knocked down walls in Crete over 100 miles away!! Historians believe these giant sea waves were what caused the mysterious end of the great Minoan civilization in the Mediterranean.
Questions
1. What caused great civilizations in the Mediterranean to disappear about 1400 B.C.?
A great volcanic eruption.
2. What is a caldera?
A bowl shaped depression caused by the magma chamber under the volcano emptying during an eruption and the volcano falling into the magma chamber because to its own weight.
3. What caused the production of a huge tsunami over 300 feet tall?
The huge tsunami was caused by the top of Santorini collapsing. This caused the large caldera to form.
Volcano Activity
Materials:
- 1 plastic bottle of seltzer of soda
- 1 small bottle of food coloring
The teacher should conduct the following experiment. Wearing safety goggles and old clothing is advised. The experiment could ruin clothing and hurt unprotected eyes. Follow the steps below having the students write down what they see.
- The teacher will pour out approximately 3 cups of seltzer or soda from the bottle. Show the students the bottle before it is opened explaining that the gases dissolved in the liquid are under much more pressure than gas outside the bottle. As the bottle is opened the gas (Carbon Dioxide) will be visible as it escapes creating bubbles.
- Add 10 drops of red food coloring
- Put the plastic cap back on the bottle
- Shake the bottle profusely
- Hold the bottle over a sink or drain- tell the students that the liquid inside the bottle represents magma, which is molten rock and gas inside the Earth.
- Turn the cap slowly allowing the "lava" to erupt slowly-tell the students that as magma escapes to the surface it is then called lava.
The teacher should explain that the liquid has dissolved gases in it (Carbon Dioxide), just as magma has many dissolved gases in it. When the bottle is not open the students will not be able to see the gas because the bottle maintains the higher pressure. When the bottle is opened the students will see the gas escape. The liquid will erupt because it is under more pressure than the outside environment. When magma rises in the conduit the pressure falls as it nears the surface of the Earth. The lava will escape violently evening the pressure. When a volcano erupts the lava may be very frothy from the escaping gases. This is true especially if the magma has a high gas content. The most violent eruptions are due to a great build up of pressure from magma that has a high gas content. Magmas with little dissolved gas usually do not erupt violently.
Lava Dome
Materials:
- Toothpaste in a tube
- Cardboard
- Scissors
Cut a hole in the cardboard so that the neck of the opened toothpaste tube fits into the hole. Squeeze the tube lightly so that a little toothpaste comes out then stop. Explain that the toothpaste is very thick and pasty like felsic lava is. This is the same lava that has built the lava dome in the crater in Mt. St. Helens. Squeeze the tube again and stop, explaining that the dome was built very slowly with these same starting and stopping motions. The dome grew for seven years and has basically halted its growth as of 8/20/95.
The dome that is in the crater in Mt. St. Helens today is not the only dome that has occupied this space. Another dome grew during the first month after the original eruption but blew up in June of 1980.
Continue the same pattern of squeezing and stopping until the students understand the concept of dome growth.
Lava Activity
Modified and adapted from John Farndon's book "How the Earth Works"
Flowing Lava
Materials:
- 4 plastic jars
- 4 spoons
- fine grained sand
- stop watch
- 4 plastic plates
- 1 tablespoon
- molasses
- liquid dish soap
- shampoo
- vinegar
Part 1
The students will need their science notebooks, pencils, and stop watches ready. One student will measure one tablespoon full of one of the liquids. They will slowly pour that liquid onto a plastic plate. Another student will time how long it takes for the liquid to stop spreading. Repeat this procedure with the other three liquids.
The liquids that have the longest spreading times have the highest viscosities. Tell the students there are lavas with very low viscosities (very thin and runny) and lavas with very high viscosities (thick and pasty). There are also many different lavas in between. Low viscosity lavas are found in Hawaii and Iceland and are usually not violent. High viscosity lavas are very violent and erupt with little or no lava. High viscosity lavas shoot pyroclasts such as pumice, cinders and ash high into the air.
Part 2
Have the students add one teaspoon of sand to one cup of the four liquids used in part 1. Stir the mixture thoroughly. Have the students repeat the pouring and timing portion as in part 1. Have all students record the times and compare Part 1 to Part 2 times.
Explain to the students that lavas with a high silica content (sand and quartz) have high viscosities (aa) and lavas with low silica contents have low viscosities (pahoehoe)
Add sand to a cup of molasses until its viscosity is so high that will not flow. Spoon the mixture onto a dish and explain that they have just created a lava dome.
High or Low Viscosity
Materials:
- 2 plastics jars
- molasses
- water
- 2 straws
Fill a small plastic jar to within one inch of the rim with water and the other jar with molasses. Put one straw into each jar. Have one student blow bubbles with the same pressure. Record what happens.
The students will see rapid bubbling in the water because the water has a low viscosity. This is what pahoehoe lava is like. The gases escape quickly from the low viscosity lava and usually are not very violent. The students will see a slow bubbling from the molasses because of its high viscosity. Lava with a high viscosity will hold a lot of gas and will loose the gas as it nears the surface of the Earth and the pressures become lower (like opening a bottle of pop and releasing the pressure). These magmas erupt violently frequently.
Floating Rocks?
Materials:
- Pumice
- Clear plastic container
- Water
Float pumice in a container full of water. Have the students draw what they see. Show the students the holes in the pumice explaining they were formed as the rock hurtles through the air.
Atlantis And Erupting Volcanoes
Arnie Cerny 9th grade Earth Science
For this activity, I kept the students together for the entire class period. I started off the period demonstrating to the entire class the erupting volcano activity. We discussed terms, such as, magma versus lava, explosive eruptions, types of lava, vents, etc. The students loved the explosive eruption (it was pretty messy). As an additional demonstration, I wanted to use the chemical (I don't know what it is) that when lit, ignites and puts out a grey cinder cone. I remember my high school physical science teacher doing this but I can't remember what chemical it was. I hope someone knows this chemical (it's orange) because it produces a nice cinder cone!!
I also demonstrated the lava dome building with toothpaste activity. I would recommend practicing this before demonstrating to the students. We had a class discussion of felsic lava, Mount St. Helen's, comparison to Hawaii, etc. The demonstration went very well. A student brought up the analogy of leaving the lid off the toothpaste and how the toothpaste dries up (like lava) causing an explosive eruption when you squeeze!!!
Both activities went very well. I made no major modifications from my original plans. The students were very enthusiastic and stayed energized throughout the activity. They appeared to like both activities equally. I thought the results of the demonstrations and the student responses far out-weighed the time I put into the preparation. The lesson got the students excited about upcoming activities and the test results showed that they comprehended the concepts very well.
These demonstrations were appealing and caught the students attention. These demonstrations proved to be more educational than notes or discussion alone.