In 2005, we went from Monteverde (cloud forest) to the Arenal region.  That year, aside from a peak at tropical rainforest in the Rincón de la Vieja region, we had not really seen much in the way of tropical lowland rainforest and we became more acquainted with that forest type in the Arenal region as well.

The image above, taken from a faded 3-D map on the wall of the Hotel San Bosco, shows the relationship of several stops on our trips.  #1 shows the location of La Selva, a field station in the tropical lowland rainforest.  #2 is Santa Elena and Monteverde, the location of the cloud forests high in the mountains.  Fortuna is #3.  Note all the protected areas between La Fortuna and Santa Elena.  A good portion of this is the protected area around various active volcanoes; much of the rest is the Monteverde Reserve and the Childrens' Eternal Rainforest.  You can also see Lake Arenal on the western side of the volcano; the lake is man-made and backs up water which would normally flow down the eastern slope to the Caribbean.  This allows the water to be diverted to the drier Guanacaste Province to the west; electricity is generated at the same time.  High winds in the area also make windfarms possible and make the lake a popular site for windsurfers.  The rebuilt town of Arenal lies to the north of the lake, well away from the volcano. 

In 2005, we made the approach to Arenal from the west, coming down the mountain from Santa Elena and Monteverde.  Here, rather than continued by road the considerable distance around Lake Arenal, we boarded boats to cross the lake directly.  Arenal, erupting, is in the background.

Loading the boat.  We were, of course, traveling with all our clothes and equipment at this point.

A view of the boat during the crossing, which took about an hour, compared to 2 or three hours it would have taken by road.  Some of the bypassed roads were paved by the time of our 2007 trip.

The volcano was noticeably different in 2007 as opposed to our first views in 2005.  The active vent had moved; the vent nearer to La Fortuna (the foreground of these pictures) was not nearly as active; everything was happening at the vent that was further away.  That vent, in turn, was much more massive.  It was now noticeably taller, and the slopes were beefed up as well.  The animation above and the 2005/2007 images to the left illustrate this.

We also noted more eruptions in 2005; it was not unusual to hear an eruption every hour or so while we were in La Fortuna.  In contrast, there were only a few noticeable eruptions during our stay in 2007.

These images show the mountain as seen from the town of La Fortuna.  Many of these pictures were taken from the upper-level observation deck at the Hotel San Bosco.

The pictures above and to the right were taken with a telephoto lens, and show the summit.  The closer vent has developed some green vegetation; there is less vegetation on the more active vent.

Left:  A view of a small eruption.  Below:  the summit at night in 2005.  Because there was so little light, a long exposure was needed which tended to blur the clouds and the lava at the top.

Right:  The church San Bosco stands in the shadow of the volcano.  The town of La Fortuna used to be called San Bosco; it was renamed after a major eruption spared the town. The town of Arenal had to be relocated; this was a good thing since it would have been submerged under the lake even if the volcano hadn't damaged it.

Left:  The volcano in the backyard.

The volcano with a small eruption at sunset.  The peaks to the left of the volcano were formed by earlier vents; as seen in this image the active vents here seem to be moving from the left side of the picture to the right (over thousands of years).

In both years we went into the national park at the base of the volcano for a hike.  To the left, and below, the group in 2005 unloads and crosses a stream coming down from the summit.

Below, the 2007 contingent  hikes in from the opposite end of the trail.  Note the tall grasses and the sandy volcanic soil.  "Arenal" means "sand", and this volcano produces a coarse volcanic sand that dominates the local soils.

As the signs reminded us, this is an area of active volcanism.  The rumble of the volcano was ever present, even if the summit of the peak was in the clouds during most of our two hikes.  The 1968 eruption was the big one that spared La Fortuna.

Right:  Risk of a different type of burn.  One of the students missed a few places with the sunscreen and got a terrible sunburn which was weeping through his shirt on the hike.

Our best views of the mountains and the lake came from the sparsely vegetated lava flow of 1992 (the vegetation you see growing here had developed since 1992).  At times, the mountaintop would be visible through the clouds that were normally present there.  Also, in 2007 this was our best chance to see lava as the active vent was on this side of the mountain (and away from La Fortuna, where we were staying).  The students took the opportunity to climb outcroppings and get photographed with the volcano in the background.  In the photo below, note how far the lava had traveled!

Zooming in on Justin from the picture to the left.

Left: " I'm King of the World!"

High on the slopes (when the clouds lifted) we could see hot rocks rolling down the side of the mountain.  The volcano is so steep it is almost impossible for the lava rocks ejected from the vent to remain in place; some of them have to roll down and thus build up the flanks of the mountains.  Most of the slope at those elevations is volcanic ash and the rocks kick up a good bit of dust as they fall.  There is video of this below.

The area we hiked through had some interesting biology as well.  A species of orange orchid (above) was common on the 1992 lava flow.  Many people don't recognize that orchids as a group are highly adapted for living in tough conditions - as epiphytes on trees, for instance, or in bogs, or, in this case, on sun-baked lava flats.

The Collared Acacari (above right) is a toucan-relative whose large beak is used to remove fruit from the trees.  We saw a whole flock in 2005.  

Right and Below:  Perhaps the most fascinating thing we saw were the Cecropia Ants (yes, I know, but I'm an entomologist, and I'm the one determining what is fascinating here)!  Like the Acacia trees we saw at Santa Rosa, the Cecropia trees recruit ants to live in them and protect the tree.  The ants drive off herbivorous insects, attack herbivorous vertebrates, and remove epiphytes and competing plants.  Their wastes also provide a lot of nitrogen to the plant.   The plant provides them with housing (inside hollow stems) and gylcogen-rich Muellerian bodies.

These two photos show the interaction between the ants and the trees.  To the right, and ant is approaching the entrance hole to the hollow stem.  Interestingly, the spot where the opening has been made by the ants starts out very thin - tha ant has little to chew through - and this part of the stem does not contain the latex that protects the plant from chewing insects at other points.  The ant approaching the entrance is bearing a Muellerian body it has picked up.  Note the guard ant in the hole.

The photo below shows ants harvesting Muellerian  bodies from the base of the leaf petiole.  There are thickly packed hairs (trichomes) in this region, and I'm guessing the Muellerian bodies are modifications of these trichomes.

Click here for a video of a monkey feeding on cecropia ants.

How effective are the ants at protecting the trees?  It's hard to tell.  Most of the Cecropia trees we saw had leaves riddles by holes apparently made by insects, and we saw sloths feeding in Cecropia trees.  It's something like the milkweed plants in Ohio - they have a nasty set of chemical defenses, but also a whole host of insects specialized to defeat those defenses.

Click here for more on Cecropia Ants

With the volcano behind us we could turn and see Lake Arenal.  This man-made lake was formed by a dam that blocks the normal flow of the water down the eastern slope to the Caribbean.  The raised water level allows the water to be re-directed to the drier Guanacaste Province, where it can be used for agriculture and urban uses.  When the lake was formed, it covered the former site of the town of Arenal, which had been damaged by the 1968 eruption.

Right:  The Volcán Arenal Observatory, ideally located to monitor the volcano (but hopefully a safe distance away???).

We took a day hike in 2007 to the Catarata (waterfall) Rio Fortuna.  This waterfall is formed by water draining off the volcano and adjacent mountains.  Several web sites put the height at 70m, but that height (230 feet) seems a bit high, at least for the lower portion visible at the pool.

The hike down to the pool is through some very lush rainforest.  The pool was pleasantly cool to swim in (although one was very sweaty by the time you hiked back out).  The rocks were quite slippery, but we enjoyed scrambling around.  

We took taxis up to the entrance and hikes the 5km or so back down the hill into La Fortuna.

More views of Volcán Arenal on the La Fortuna page!