Thermal Activity at Miravalles Volcano in Costa Rica

After the previous day’s long hike at Arenal Observatory, Bob and I decided to indulge in a leisurely drive and go a little further afield from La Fortuna to see the Miravalles Volcano in Costa Rica.

Miravalles Volcano is the tallest volcano in the Guanacaste Mountain Range with an elevation of 6,637 feet (2,023 metres).  It was calling our name!

What had us venturing to Miravalles besides the thermal hot springs near the volcano, was, in particular, the Las Hornillas Volcanic Activity Centre.  There, we would be able to walk inside an active crater!

The 2.5-hour drive into Guanacaste Province slid by quickly.  The landscape as we drove from La Fortuna was at first dominated by rolling farm fields.

Closer to Miravalles Volcano, rugged landscapes provided a hint of previous volcanic activity in the area.

As usual, it was the flora and fauna that had us stopping occasionally for a snapshot, such as this Ctenosaur that we spotted edging up to a fence.

A Ctenosaur is more commonly referred to as a Black Ctenosaur Iguana.

Las Hornillas Volcanic Activity Centre is located in the foothills of the Miravalles Volcano. The volcano is a dormant stratovolcano typified by its cone shape and steep sides.

Miravalles Volcano’s last eruption was a minor explosion of steam in 1946, but the underlying geothermal activity is what accounts for the profusion of bubbling mud pots, fumaroles and hot springs over the surrounding area.

Off we went to view the features from a series of strategically-placed walkways.

Ongoing geothermal activity is the result of leftover magma below the surface.  It heats underground streams as they pass over scalding hot rocks turning the water into steam.

The vapours carry hydrogen sulphide as they rise to the surface.

The noxious gases escaping from the fiery depths pop and hiss at the surface where they burst through hot pools of water or mud.

The corrosive effect of the steam was evident on the steel cores of the guardrails.

Although the idea of sitting in a hot spring heated by thermal activity is appealing, Bob and I were glad that our exploration of the crater kept us well away from the fumaroles venting steam.

Fumaroles are used to predict volcanic activity, but they are also characteristic of the end of volcanic activity.  Some fumaroles cease activity soon after an eruption while others continue to spew heated steam for decades.

Sulfuric gases, when they have a chance to cool at the surface of the earth, solidify into yellow sulfur crystals.

Across the fumarole field, different mineral elements have oxidized as they hit earth’s atmosphere creating various colours that brighten the landscape.

It would be antimony- or arsenic-laden steam wafting over some of the rubble that lends it an orange colour.

Nearing the top of the crater, Bob’s attention was drawn to a flurry of activity in some nearby trees.

A couple of White-throated Magpie-Jays were quietly foraging in the shadows.  We thought, “How beautiful are these birds with their striking blue plumage and a dashing plume on top of their heads”.

When one of the Jays began to vocalize, we realized why these birds are often maligned for being noisy and gregarious.

From one vantage point, I had a view back towards the main centre where we would find the mud baths and hot springs.

Before we got there, though, we stopped in our tracks when another huge Black Ctenosaur Iguana crossed our path.

Often confused with Green Iguanas, Ctenosaurs lack the head spines and crests.  Their bodies are darker in colour, as well.

Also called Spiny-tailed Lizard for obvious reasons, a Black Ctenosaur Iguana has whorls of intimidating spines covering its long heavy tail.  Its sharp claws facilitate a Ctenosaur’s ability to climb trees and no doubt contribute to its reputation as the fastest-running species of lizard in the world.  They are able to reach speeds of 34 kilometres per hour.

Bob and I didn’t approach the Ctenosaur, but they are of no threat to humans since their diet consists mainly of insects and vegetation.

In the near distance, Bob and I could see another visitor covered in mud at one of the mud baths.

Mud baths are touted as having therapeutic benefits because of the high mineral content of the viscous mud.  I was intrigued by the mud bowls floating on the surface of one such mud pot.

It seemed that the basins were used to scoop up the mineral-rich mud so that it can then be painted onto a person’s body.

Although the mud baths were popular with some guests, Bob and I decided not to avail ourselves of the opportunity.

Instead, we focused on a beautiful butterfly that lit on a nearby piece of volcanic rock.  Banded Peacock Butterflies are found in Texas, Mexico and throughout Central America, but for reasons unbeknownst to me, the species is studied the most in Costa Rica.

Because Banded Peacock Butterflies are not toxic to predators, they are routinely eaten by birds, lizards, and frogs among other creatures.  We were thinking that this one just might become a snack for the Ctenosaur Iguana.

Wandering further, we came upon a series of hot pools, one draining into the other.

An aqueduct similar to those that we have seen utilized in Peru was quite efficient at moving water from the hot springs to the pools.

Before visitors enter any of the hot pools, they are required to shower in outdoor facilities to remove any mud from their bodies.  The thermal pools certainly looked inviting with an atmosphere and ambiance to match.

What a surprise when a gorgeous Peacock came strutting its way through a thicket of bushes.  Although not native to Costa Rica, this one sure lent a modicum of elegance to the relaxing air of the hot pools.

Although technically called an Indian Peafowl, the males are referred to as Peacocks while a female would be called a Peahen.

In the years since Bob and I visited Las Hornillas Volcanic Activity Centre, it has been incorporated into Miravalles Jorge Manuel Dengo National Park.  It has now been declared a protected area due to the natural resources it contains and for its potential for research and conservation.

Bob and I were ready to head back to La Fortuna after our afternoon of exploration.  We were glad to have had such a wonderful view of Miravalles Volcano gracing the horizon with its majestic presence.

Frame To Frame – Bob and Jean