I’ve been fascinated with the scenario of an active volcano poking above the jungle. Back in 2009, I experienced it when I visited Costa Rica and watched Volcan Arenal for 4 nights at the Arenal Observatory Lodge observing incandescent lava rocks tumbling down the flanks before stopping at it’s jungle base.
We are going to take a look at two volcanoes which are also set in the jungle, Ecuador’s Reventador and Sumaco. These volcanoes lie within the foothills of the Andes on the Amazonian slope and are surrounded by tropical forests. Reventador is currently active while Sumaco is currently dormant. A year ago, I was actually in the area close to Volcan Reventador but I would not have seen a thing due to cloudy weather conditions at the time which makes sense because it was in the upper Amazon Basin and the Rio Coca valley was full of forests.
El Reventador is one of Ecuador’s most active volcanoes and not surprisingly so given that the translation in English for “El Reventador” is, “The Exploder”. This 3562m high stratovolcano lies on the edge of the Cayambe Coca Ecological Reserve and it sits inside the western part of a horseshoe shaped caldera which is breached to the east and is located uphill from the Rio Coca valley not far from the San Rafael waterfall, and the Hosteria El Reventador. The caldera itself is 4km wide in diameter and was formed as a result of an edifice collapse and also, numerous overlapping lava flows occupy the caldera floor. Some exposed older lavas can be seen at the Rio Malo waterfall on the southern end of the caldera edifice.
While the caldera is accessible by foot via a few hours hike through the forest, climbing the cone itself is not recommended given the high level of activity. They certainly don’t call it “The Exploder” for nothing!
The activity of Reventador consists of regular strombolian explosions with some effusive activity but during periods of elevated volcanic activity, the odd pyroclastic flows may occur. Historical observations of eruptions on Reventador dates back to 1541 and continues right up to present day. But the most significant eruption of Reventador occurred in 2002.
On the 3rd November 2002, an unexpected eruption with the scale of VEI 4 occurred after a 26 year repose. Apparently there were no visual signs of unusual activity prior to the eruption, only seismic activity detected on the 6th October 2002 and during the early hours of 3rd November 2002. At daybreak, local workers reported seeing a steam column rising about 2-3km above the cone before an ash plume was later observed at approximately 7:15 am. It was only at approximately 7:45 am when the eruptive activity on Reventador started to get rough when the eruption column reached 6km above the cone before drifting southwest. Explosion after explosion the eruption column reached 7km above the cone by 8:03 am and a constant roar was heard up to 8km away in distance. It was at 9:12 am when the main eruption started which eventually led to the eruption column having reached 16-17km above the cone, which resulted in the ash cloud later drifting as far away as Quito and the Andean valley, leaving a 3-5mm layer of ashfall. Pyroclastic flows were observed descending the south and southeastern side of the cone before eventually travelling along the south caldera floor, some flows overtopped the caldera rim. The longest pyroclastic flow travelled 8km out of the caldera before reaching the Rio Coca. Effects from the eruption included visibility problems, roof collapses, crop damage, the closure of Quito Airport for 8 days, and power cuts in certain areas. The eruption also threatened the oil pipeline in the area. As for the wildlife which may have resided in or around the caldera, it was apocalypse for them. During the early hours of 4th November 2002, the intensity of the eruption reduced but continued.
In the days which followed, smaller explosions continued to occur but a significant explosion on 5th November 2002 possibly generated pyroclastic flows. A lava flow broke out around 6th-7th November 2002 which was soon to become the first of many in the years to come. The biggest hazard to human lives in the area came from debris flows and lahars which had occurred in the years to come. By October 2009 there were 17 lava flows recorded since the 2002 eruption, some had travelled as far as 4-5km onto the caldera floor.
Out of the 17 lava flows between November 2002 and October 2009 which flowed the longest distances they were: lava #1 (Nov 2002), lava #4 (Apr 2005), lava #5 (May 2005), lava #9 (Apr 2007), and lava #11 (Jul 2008).
Beyond 2009, a lahar destroyed a bridge over the Rio Marker during May 2010 and a lava dome formed inside the summit crater during September 2009 before eventually growing to a height above the crater rim during late 2012. Activity of recent years includes incandescent rocks breaking off from the summit lava dome, explosive activity, lava flows, and the occasional pyroclastic flows.
As we move on from Reventador we go 32 miles south where another volcano within the upper Amazon Basin is located, Sumaco Volcano. This isolated 3990m high stratovolcano rises above the forests of the western Amazon Basin. Unlike Reventador, Sumaco is a dormant volcano which supposedly had one historical eruption sometime between 1865-1925 but it has produced alkaline rocks such as Tephrite, Basanite, and Phonolite, different from the volcanic rocks in the main Andean chain. The reason for this is because magma was formed at great depth and is further east from the Andean chain volcanoes.
An older Sumaco Volcano (Paleo Sumaco) collapsed following a violent eruption leaving a collapse scar and avalanche deposits to the east. Ashfall in surrounding areas from that eruption came as thick as 10m. The present cone was constructed within the collapse caldera. A parasitic cone, Guagua Sumaco is present just to the southeast of the main volcanic cone. Meanwhile, a significant amount of pyroclastic deposits is present to the south of the volcano.
The volcano and surrounding area comprises of 4 eco zones: low montane evergreen forest, montane cloud forest, high montane evergreen forest, and herbaceous high wetland. These host a biodiversity of flora and fauna including orchids, tapirs, armadillos, the Spectacled Bear, different species of birds, butterflies, frogs, monkeys, and many more.
Being in good physical shape is required to climb the volcano which is said to take three days to ascend, and two days to descend. Different weather conditions such as rain, humidity, coldness, and high winds at the summit may occur.
As a bonus section I thought I’d give a quick run through of the other attractions of the area.
Volcan Pan de Azucar is an eroded extinct volcano which lies on the southwest edge of the Sumaco Napo-Galeras National Park to the north of Volcan Sumaco. Little is known about this volcano given it’s isolated location deep in the forest.
Alto Coca Reserve is located within a forest up on the plateau south of the Rio Coca. You can actually spend a few nights here observing the flora and fauna, and watching the activity of Reventador across the valley.
Cascada Rio Malo is an impressive waterfall located to the south of Reventador Volcano which can be visited via a turn off from the main highway.
And finally we have the Cascada San Rafael, Ecuador’s tallest waterfall located to the east of Reventador Volcano. Recently, the flow of water was disrupted by the newly constructed Coca Codo Sinclair hydroelectric dam.
Video credit: Mark Thurber.
Global Volcanism Program
Mapping and Measuring lava volumes from 2002 to 2009 at El Reventador Volcano, Ecuador, from field measurements and satellite remote sensing – M. Fernanda Naranjo, Susanna K. Ebmeier, Silvia Vallejo, Patricio Ramón, Patricia Mothes, Juliet Biggs, and Francisco Herrera.
Sumaco Ecoroute Guide – Theofilos Toulkeridis, Vlastimil Zak, Florencio Delgado, Andrés León-Reyes, Xavier Silva, Fabián Burbano, and Arnaldo Rodriguez-Green.