June 2014

Hummingbird Violet Sabrewing

Hummingbird
Violet Sabrewing

 

 

 

 

 

Volunteers:

When people give their time, energy, and skills to volunteer at Cloudbridge they are helping the environment by contributing to the reserve’s many needs.  Usually the volunteers also benefit personally by gaining new interests and  learning new skills.  They have the chance to develop new friendships with other volunteers and people in the community.   For those who are looking for a science based career, the experience of helping out with biological surveys, tree planting, vegetation control or any of our other ongoing projects can boost their options for career opportunities.  Some people come to volunteer in order to diversify their life and have an adventure.  What ever the reason we hope each volunteer leaves the reserve with a sense of achievement.

The organization ARO from Quebec Canada brought groups of volunteers to Cloudbridge in June.  They eagerly helped with road improvements, tree planting and vegetation control.  They had the opportunity to visit the waterfalls and hike some of the trails to see what a tropical cloudforest is all about.

ARO Volunteers

ARO Volunteers

The volunteers moved a large sheet of plastic to cover an area that has been taken over by invasive grasses.  This practice is used in order to kill the grass under the plastic instead of using herbicides.

Hauling cardboard up the mountain

Hauling cardboard up the mountain

Cardboard is recycled as mulch around the newly planted trees.  There are 3 main benefits:

1. It keeps the weeds down and assists the workers in general maintenance around them.

2.The mulch holds the moisture in the soil during the dry season.

3. It encourages the worms to migrate into this area under the cardboard where they improve the soil conditions for the young trees.

 

Improving our very rough road.  Hopefully this will make the drive to the reserve a little better.

Improving our very rough road. Hopefully this will make the drive to the reserve a little better.

 

Group photo of the ARO volunteers.

Group photo of the ARO volunteers.

 

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Heath from Australia and Kirk from the US are here until mid July.

They are both doing tree monitoring on Stephan’s plot, leading groups of ARO volunteers,  planting trees, redesigning and cleaning the tree nursery, and an assortment of other tasks.

Heath and Kirk

Heath and Kirk

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Max Cunningham

Max Cunningham

My name is Max Cunningham, and I’m a graduate student at Columbia University’s Lamont-Doherty Earth Observatory.  I spent the last three weeks at the Cloudbridge Reserve and near the summit of Cerro Chirripó, studying the various erosional processes that have shaped this beautiful landscape.

 

I’m a geologist by trade, with a focus on the interplay between climatic conditions and the processes that cause erosion.  Recently, I’ve paid particular attention to erosion processes in glacial regions, especially in valleys thawing out of a frozen state.

A glacier is, in some ways, analogous a snow-fed river of ice; in order for a glacier to fill a valley, temperatures near the glacier’s “headwaters” must stay below freezing over centuries or millennia.  Erosional features near the summit of Cerro Chirripó have clued geologists into the fact that glaciers once persisted here in Costa Rica, but some important questions remain: how long ago was the climate in Costa Rica so cold that glaciers eroded the country’s highest peaks?  How much ground did these glaciers cover?

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Valle de Los Lagos: Some features that glacial geologists look for are U-shaped valleys floored by large lakes. These are distinct characteristics of glacial erosion: ice flow creates the U-shape, and lakes form when glacial meltwater fills erosional depressions near the glacier bed.

 

Back at the Lamont-Doherty Earth Observatory we hope to provide answers to these questions with chemistry.  Specifically, we plan to use Cosmogenic Radionuclides to measure how long ago rocks once covered by glaciers were exposed to the atmosphere.  A Cosmogenic Radionuclide is a rare isotope that’s produced by the interaction between atoms in rocks and cosmic rays, high-energy particles that bombard our atmosphere every day.  We can tell how long a rock has been exposed to atmospheric conditions (rather than covered by thick glacial ice) by measuring the concentration of Cosmogenic Radionuclides in the rock.

I spent a lot of time my last three weeks bushwacking through valleys at Cerro Chirripó, searching for the perfect rocks to sample for Cosmogenic Nuclide dating.  I ultimately found ten samples that I think will give us an idea of how extensive, and how long ago, glaciers eroded Cerro Chirripó.

Boulders in Valle de las Morrenas: In order to carry out Comsmogenic Radionuclide dating, we need to make certain assumptions about the rocks we sample, especially in regard to the rock’s emplacement by glacial erosion.  We like large boulders that sit atop the crests of moraines, linear mounds of cobbles deposited during glacial retreat.

Boulders in Valle de las Morrenas: In order to carry out Comsmogenic Radionuclide dating, we need to make certain assumptions about the rocks we sample, especially in regard to the rock’s emplacement by glacial erosion. We like large boulders that sit atop the crests of moraines, linear mounds of cobbles deposited during glacial retreat.

In the proverbial “big picture,” a better understanding of the timing of glaciation in Costa Rica will give us information about climate conditions in the past, and put into perspective the magnitude of climate change today.

Additionally, Cerro Chirripó offers insight into how glaciers influence the erosion of landscapes.  Walking along the Cloudbridge Reserve’s trails with volunteers Heath, Julia, Elouise, Kirk, and Janine, I saw evidence of rapid erosion processes.  Perhaps the most striking was the spectacular Rio Chirripó Caldron Falls, which cuts through the bedrock in the Cloudbridge Reserve.  In order to erode rock, especially rock as strong as the Chirripó Granodiorite, rivers must have a tremendous amount of energy.

Caldron falls at the far end of the Cloudbridge Reserve bordering Chirripo National Park: This high-energy stream, fed by incessant Costa Rican rainfall, has so much energy that it erodes through the strong Chirripó Granodiorite, a crystalline rock.  The absence of similarly powerful rivers near the top of Cerro Chirripó is surprising.  The waterfall here is about 1 km from the Cloudbridge Reserve entrance.

Caldron falls at the far end of the Cloudbridge Reserve bordering Chirripo National Park: This high-energy stream, fed by incessant Costa Rican rainfall, has so much energy that it erodes through the strong Chirripó Granodiorite, a crystalline rock. The absence of similarly powerful rivers near the top of Cerro Chirripó is surprising. The waterfall here is about 1 km from the Cloudbridge Reserve entrance.

Rivers typically flow along steeper gradients at higher elevations, which translates into higher erosive power.  Surprisingly, this is not the case in old glacial valleys at Cerro Chirripó.  The rivers I observed near the summit seem to impose very little change on old glacial valleys.

I suspect that catastrophic processes that occur during deglaciation alter river erosion dynamics so severely that not much erosion takes place after glaciers bulldoze through a valley.  For instance, I identified a few giant landslides on top of Cerro Chirripó that were likely induced by retreating glaciers.  These landslides can dam rivers, sapping away their erosive power.

In this way, glacial erosion, or erosion conditioned by glaciers, may act to “fossilize” landscapes.  Because of its location in the perennially warm tropics, Cerro Chirripó underwent this fossilization process long ago.  Perhaps warming glacial valleys today can expect the same treatment.

 

Landslide in Valle de los Conejos: Large landslides can dam rivers, preventing future erosion.  On top of Cerro Chirripó, I observed several large landslides.  Here, large blocks the size of a small house stand as monuments of a catastrophic landslide at Cerro Chirripó.

Landslide in Valle de los Conejos: Large landslides can dam rivers, preventing future erosion. On top of Cerro Chirripó, I observed several large landslides. Here, large blocks the size of a small house stand as monuments of a catastrophic landslide at Cerro Chirripó.

 

I had a phenomenal time exploring San Gerardo de Rivas and Cerro Chirripó with the volunteers at the Cloudbridge Reserve.  I enjoyed the opportunity to learn more about the wildlife lurking in the vast wilderness around Cloudbridge, and to learn about reforestation efforts.  As a geologist, I was surprised by the apparent connection between patterns of plant growth and erosion processes here, both near the Cloudbridge Reserve and higher up on Cerro Chirripó.  After processing this batch of samples, I hope to explore more the link between landscape erosion and the unique biology of Costa Rica.

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Camera trap photos:

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camera trap2

camera trap

 

 

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