Showing posts with label Lava. Show all posts
Showing posts with label Lava. Show all posts

Wednesday, September 22, 2010

Magma, Lava, & Tephra



Arching fountain of a Pahoehoe approximately 1...Image via WikipediaSince it is still Happy Volcano week I thought I would describe the different between three terms you might here during your visit to Costa Rica. First of all one that people always ask is what is the different between Magma and Lava?

They are both motlen rock but Magma is located in magma chambers below the Earth's surface and lava is molten rock that has reached the Earth's surface. The tempature of mamga is between 1300F - 2400F and lava is 1300F 2300F very similar. Lava probably comes from the Latin word "Labes" which means to fall or slide which best describes its action when it reaches the Earth's surface.

Now a third fragment you might not be too familiar with but you should know when visiting Costa Rica is Tephra. Tephra relates very much to magm and lava. Lets look at it like this. Lava is to magma in an extusive form what Tephra is to magma in an explosive form. What this means is that Tephra is fragment material produced by volcanos which becomes airborne. This is very common in history in Costa Rica. We always here have coffee crops were destroyed from acid rain and the present Turrialba volcano activity. Ash can travel for miles into the stratosphere and large amounts of Tephra can reflect light and heat from the sun and tempatures on the Earth can drop just from the eruption of a volcano. Now thinking for the last post I wrote at the start of volcano week the Tephra material is a result of what kind of eruption that is very common in Costa Rica? Pyroclastic Eruptions! Very good I can see your learning.  The picture in this blog is not of Costa Rica but I liked it so much I thought I would share...
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Thursday, September 16, 2010

Poas & Turrialba Volcano Ready to Erupt




Scheme of a phreatic eruption.Image via Wikipedia
PHREATIC  ERUPTION

Yesterday on September 15th 2010 I was driving to Pacuare River enjoying the view of the smoke of the Turrialba Volcano. I was remembering a few years back when we had a group scheduled to hike to the Turrialba volcano and we had to cancel because the volcano began some activity. The group was pretty bummed and we brought them to Irazu and they just didnt understand why they couldnt go to Turrialba. First of all for an adventure company like us, safety first. Having a group on the side of an active volcano while it erupts, yes, it is exciting and quite the adrenaline rush but once it hits the headlines it really isnt good for business. As a guide you explain what can happen and some just go on to think it can ever happen to them.

After seeing the Turrialba Volcano yesterday and seeing how the activity has grown over the last 18 months and now the Poas volcano has picked up quite a bit of activity I thought I would explain why we as a company dont hike up the side of the Turrialba volcano with clients these days and how Poas volcano might soon be closed more days than open.

The Turrialba volcano continues to release certain gases through its crater which indicate that there is a body of magma below releasing these gases. The danger at the moment is not that the magma is going to come up all at once and do what you would imagine your average volanic eruption to be with lava shooting up and pouring down it's side like Arenal volcano. The danger is what is called a Phreatic eruption.

A Phreatic eruption (PICTURE EXPLAINS PERFECT) is when the area of magma makes instant contact with surface or ground water causing instant evaportation and explosion of steam, ash, rock, and a volcano bomb. This is what we saw happen to Mt. St. Helen in 1980. To say the least this would be nothing pretty to be standing anywhere near taking a picture with your "I love CR t-shirt". These eruptions can vary in size and most result in acid rains that affect nearby agriculture.
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