Introducing Volcano Baru (Vulcan)

[BrickFielder]

Introduction
My intention is to produce a series of articles (depending on interest) which introduces ideas about volcanic and earthquake activity. I want to go slightly off the beaten track to explore oddities, volcano hazards, analysis methods, Wonders and Mankind’s impacts. Keep in mind I am not expert (corrections gratefully received), but hopefully these will at least give a flavour of some different places in the world and provide a few minutes escape from people’s troubles.

Introducing Volcano Baru

 

Reason for Interest
Volcano Baru is a volcano with a history of explosive eruptions. It has the town of Volcan within reach of pyroclastic flows and the town of Boquete within reach of lahars. It has had recent swarms of earthquake activity and warrants close monitoring. It has been hypothesized that Volcán Barú experienced an eruption with estimates of ejected material ranging up to to 100 km3. Debris-avalanche deposits and lahars extend as much as 90 km away from the collapsed edifice, reaching the Pacific Ocean. What really piques my interest in the complicated tectonic environment or maybe it is the shangri-La rainbow town of Boquete.

The Setting
Barú volcano (also called Volcán de Chiriqui) is an active volcano 35 km east of the border to Costa Rica in the Talamanca Range of western in Panama. The complex, mainly andesitic stratovolcano is Panama´s highest peak and the forested volcano summit hosts many communication towers.  The volcano slopes are known as the bread basket of my country and The highlands of Chiriqui on my slopes produce some of the most unique coffees in the world.

The volcano towers above the small town of Boquete nestled in the cool highlands of the western Panama Chiriqui province. Boquete is described as a Shangri-La of tumbling streams, mountains clad in rain forest, abundant in orange groves and coffee plantations, with a picture-postcard town chockablock with flower gardens. With its cooler, fresher climate to the rest of Panama, it’s known as ‘The Valley of Eternal Spring’. It’s home to Panama’s most famous coffee region, plus a large number of US retiree expats. To residents of Boquete Panama, frequent rainbows are the product of the bajareque, a delicate drizzle that sometimes accompanies the north winds that blow down from the mountains. The rainbows arch, often in multiples, over the Valley of Flowers and Eternal Spring, aptly named due to the town’s vast array of exotic flora and its balmy weather that rarely registers above 80 or below 70 degrees Fahrenheit. Rock climbing is now one of the fastest-growing sports in the region. very year in January, the district of Boquete receives about 100,000 visitors who come to this region to stroll though the many pavilions of the famous Flower and Coffee Fair.

Just outside  Boquete town is Bambuda Castle the only castle in Panama. 

Perhaps the only thing that differentiates the seasons is the rainfall that occurs during the summer (roughly May through October) and ceases during the winter months (November through April).  

Commonly seen species in the area are the famous Quetzales, Black Guan, Black-thighed Grosbeak, Black and White Hawk-eagle, Toucans , Tanigers along with jaguars, pumas, ocelots, jaguarundis, and margay. You may also find the mischievous coatimundi, armadillos, tapir, sloths & monkeys.
 

The Tectonic environment
Volcán Barú lies along a complex plate boundary inboard of the Panama Triple Junction located in southern Central America, near the border with Panama and Costa Rica. The Panama Triple Junction (Cocos-Nazca-Caribbean) represents the point that abruptly separates the thick and rapidly subducting Cocos plate to the northwest from the thin and obliquely subducting Nazca plate to the southeast along the Central American convergent margin.

The Cocos plate, to the northwest of the triple junction, subducts rapidly under the Caribbean plate and Panama microplate and exhibits significant changes in character along strike. The Cocos plate systematically decreases in dip laterally from a steep slab in the northwest outboard of Nicaragua, to an almost horizontal slab in southern Costa Rica and Northern Panama. The Nazca plate slab, in contrast to the adjacent Cocos plate, is likely steeper, contains thinner crust, converges at a much slower rate and subducts at a highly oblique angle. The large limestone contribution at Volcan Baru may reflect the large contribution of pelagic carbonates to the slab flux. 

In the Volcan Baru region there is the edge of the shallow subducted Cocos plate and a combination of extension and steeper subducted Nazca Plate. An extremely complicated and unusual tectonic environment.

The Volcano
Its summit, 3,374 m altitude, towers about 2,000 m above populated valleys to the west and about 2,400 m above those to the east. More than 10,000 people live in areas immediately adjacent to the volcano, where the hazards from future eruptions are greatest. The heavily populated Pacific coastal plain, crossed by the Pan-American Highway, lies 30 km to the south. Volcán Barú has been built by numerous eruptions dating back several hundred thousand years. The volcano is notable for its young, large andesitic to dacitic dome complex nested within a horseshoe-shaped amphitheater carved into the older part of the volcanic edifice. Eruptions of the past few thousand years have been from vents on the summit dome.
A large 6-km-wide summit caldera breached to the west was formed by a large volcanic landslide, which created a massive debris-avalanche deposit about 9,000 years ago that extends onto the Pacific coastal plain, largely overlying a late-Pleistocene avalanche deposit. Post-collapse eruptions have constructed lava domes inside the caldera that have grown to a height exceeding that of the caldera rim. Prehistoric eruptions of Volcán Barú have repeatedly spread tephra blankets more than 100 km downwind and deposited thicknesses of 10 to 20 cm at distances 10 to 15 km downwind. Pyroclastic flows have been common during eruptions of Volcán Barú. Block-and-ash flows of the past 1,600 years have descended westward from the summit area toward and through the present-day town of Volcán. In 2008 the US geological survey highlighted a massive debris avalanche deposit described as the largest example in Central America.

The volcano was declared a national preservation area called Volcán Barú National Park in 1976, with an area of 14,325 ha (35,400 acres). One of the park’s most popular trails is the Quetzals Trail, which runs between Cerro Punta and Boquete. The trail is 8 kilometers (5 miles) long and takes you through forests and meadows, and is crisscrossed by the Río Caldera. Another popular trail is to the lost Waterfalls Trail which takes you through lush cloud forest in search of three lost waterfalls. The cloud forests on the slopes can also be explored through the Boquete Tree Trek where 4.5 km of elevated zip lines let you explore the tree canopies.

Past Eruptions
The volcano has had four eruptive episodes during the past 1,600 years, including its most recent eruption about 400–500 years ago. Several other eruptions occurred in the prior 10,000 years. Several seismic swarms in the 20th century and a recent swarm in 2006 serve as reminders of a restless tectonic terrane.

Recent Activity
In 2006, an earthquake swarm was recorded near Volcan baru. This was not the first, researchers cite at least three other seismic events of the same nature, recorded in the recent past, 1930, 1965, 1985.

Discussion
Although it is thought unlikely the volcano will experience another collapse in the near future the risks of pyroclastic flows and lahars represent considerable threat to a significant population. Perhaps the biggest under appreciated risk is ash fall which could decimate agriculture and infrastructure.