Arenal location mapKutztown Geology 2007-2008 trip to

Costa Rica
Arenal Volcano - La Fortuna

Arenal is an active volcano that's been erupting continuously for the last 40 years.  The composition of the magma is richer in silicon than the runny lavas of Hawaii, so Arenal's lavas are more viscous.  On the other hand, Arenal magmas are not as silicon rich as the really explosive volcanoes, so Arenal's continuous eruptions have been energetic, but not extremely dangerous.  Lava erupts from the crater both as a fluid flow and as volcanic bombs.

Arenal group photo

Arenal was shy the days we were visiting.  The upper half of the volcano was hidden by cloud cover.  On clear days, Arenal looks like this.  We were certainly not disappointed, though.  It's an incredible sight!

Arenal peeks through cloudsThis is the clearest view of the peak that we saw during our stay.  As you can see, it was also a quiet period during the eruption.

Arenal through cloudsAlas, this may look a little like volcanic gas and ash erupting, but it is just cloud cover. 

Hanging Bridges

Arenal Hanging Bridges

At the base of Arenal volcano, an ecotourism company built a looping path through the jungle.  The topography is deeply incised by creeks, so they had to build a series of bridges.  Rather than having the path dip down into each gully, they built high suspension bridges that allow the hiker to hike through the tree canopy. 

Leaf cutter antsThis was our first encounter with leaf cutter ants.  They are truly amazing to watch.  They form an anastomosing current that runs in two directions.  Half of the ants walk in one direction carry pieces of leaves for their nest, and the other half walk "empty-handed" in the opposite direction to go and collect more.  The ants were smart in their choice of paths, generally avoiding the human path so they don't get stepped on.

Arenal Hanging Bridges

Cassandra (in pink shirt) was timid about walking the warbling suspension bridges at first.  It is a 30-70 meter drop (100-230 feet), after all!  After the first few bridges, though, she focused her mind and conquered her fears.  Abe (in hat) apparently has no fear.

Arenal Hanging Bridges - jungle viewThis view from one of the suspension bridges gives an idea of the height of these things.  Note the bridge by the creek for scale.

Butterfly/Insect/Reptile Zoo

butterflyButterfly farms are a popular tourist attraction near many  volcanoes and national parks.  We visited the one near Arenal.  The butterfly tent was not as populated as I'd imagined, but they're in the process of developing it.

holding the pythonThe  butterfly farm near Arenal, however, has a well-stocked collection of reptiles, which I think are the owner's true love.  They house a variety of poison dart frogs, tree frogs, and lots of snakes.  They fed one of the vipers while we were there and let us hold their 100 kg (220 pound) python.

tree frogThe tree frog must be the national emblem of Costa Rica.  They are certainly beautifully colored!

red water pitcher flowerThe butterfly tent had a variety of beautiful flowers.  This water-catching flower (I'm a decent geologist, but my botany is weak!) was common in the region.

red flowerThis flower struck me as interesting because the pistils are so long.  It must be an adaptation for whatever pollinates the flower. 

La Fortuna Waterfall

columnar joints at La FortunaThe hike down to the La Fortuna Waterfall descends 600 steps cut into the steep hillside.  Along the way, one can see some nice columnar joints exposed in the cliffs.  Columnar joints are a special way that lava flows fracture during cooling.  As the solidified lava cools, it shrinks, but because it's solid rock, the rock fractures instead of flowing.  Geologists call simple fractures in rocks "joints."  These joints are shaped like giant, vertical pencils and so are called "columnar joints."

La Fortuna fallsLa Fortuna waterfall is pretty impressive.   It's worth the hike down and the little fee to take the path back helps the local economy.

swimming at La Fortuna fallsThe water is definitely very, very brisk, but tolerable to those of strong will and mind - making swimming in the river a fun experience.  Of course, since this was a geology fieldtrip, I gave a short lecture on hydrogeology at this point, but I don't think anyone heard me.  ;-)

Bridge of the Iguanas

Iguanas at the bridgeOn the drive to Alajuela (town near Poás volcano), we stopped at a roadside shop near El Puente de Iguanas (Bridge of the Iguanas). The trees were crawling with iguanas - some big orange ones like this, as well as smaller brown ones.  Iguanas here ranged up to about 4 to 5 feet in length.

Sugar Cane along the roadside

sampling sugar caneAs we drove around the country, we'd see fields along the road growing things we don't see often in Pennsylvania.  Here, we stopped to sample some sugar cane.  The cane has a diameter about that of a baseball bat.  Once one strips away the outside "bark," the fibrous inside is very sweet for chewing.  Imagine chewing on some very soft wood that tastes like sugar.  We also saw teak, palm oil, banana, pineapple, coffee, coconuts, rice, and rubber. 

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swimming at La Fortuna falls