Thursday, December 6, 2012

A Glimpse into Costa Rica's Future...

 
Costa Rica is one if the youngest sites of its kind (3 myr), with a unique geographic history and tropical landscape, a broad range of both geological and geographic activity, two coastlines (flanked by the Pacific Ocean to the west and the Caribbean Sea to the East), and an incredible diversity of terrain, biota and weather. As a part of the Central American volcanic front (a border between volcanic and non-volcanic zones that often occurs in the trench side of an island arc), Costa Rica was formed through the subduction of the Cocos tectonic plate beneath the Caribbean plate at the Mid American Trench. This also created its Nicoya Peninsula at the Pacific Rim, unique in its position directly above the seismogenic zone of a subducting megathrust. The study of geographic patterns will help project how Costa Rica’s landscape might change over the next 1,000-1,000,000 years. 


COSTA RICA 1,000 YEARS FROM NOW… 
The rapid convergence rate (~9 cm/yr) of the
Cocos plate and the Caribbean plate is the cause
of Costa Rica’s frequently occurring earthquakes
(<M 7.0), as the land’s proximity to the subduction
 trench makes it particularly sensitive to vertical
tectonic movements, as this map of Costa Rica's
 plate tectonics illustrates.
Past plate tectonic activity provides evidence of a future abrupt coseismic (an area simultaneous earthquake occurrence) uplift followed by postseismic and interseismic subsidence. A magnitude 7.7 earthquake in 1950 produced landslides, liquefaction and coseismic coastal uplift creating high inland tides. Emerging marine terraces (ancient shorelines) and uplifted alluvial fill (ancient river deposits) have been recorded. Additionally, evidence of sea level rise (~3mm/yr) suggests vulnerability to coastal low-lying coast hazards (e.g. hurricanes, landslides, storm surges, etc.).  Thus, one may expect to see an increase in the coasts shoreline, and the intrusion of deeper inland tides in 1,000 years.





 

COASTA RICA IN 10,000 YEARS FROM NOW…
Although a geologically young landform, Costa Rica’s dense volcanic population is in itself impressive, as the 100+ volcanic landscape is part of the Pacific Rim of Fire. These uplifted features range in shape from symmetrical cones rising to a single crater, sprawling mountains with collapsed calderas, stratovolcanoes like the Arenal Volcano on the left, and some lower shield-shaped outlines.
 

Violent eruptions created through deep crustal movement triggering think and viscous magma to release, often results in the production of new cones, some of the youngest being only 60 years old. Isotopic dating of surrounding and erupted material has lead geophysicists to calculate Holocene and Pleistocene uplift rates. Thus, leading us to expect that within 10,000 ears, Costa Rica’s 50,000 km² landscape will be laden with new, active, juvenile volcanos and possibly, additional craters, lakes or calderas where older volcanoes are today.




COSTA RICA 1,000,000 FROM NOW…
Offshore geophysical studies of Costa Rica’s westward coast, have identified sharp variations in uplift patterns coinciding with three distinct domains of subducting seafloor segments, each originating from distinct oceanic spreading ridges and exhibit contrasts in crustal thickness, surface roughness and heat flow. Since the cycle of subduction zone convergence is a never ending process, and the preceding findings indicating to be true in Costa Rica, in the next million years, can expect a global shift northeastward , eventually towards modern day Florida, of the area we today call Costa Rica, a vast increase in volcanic and seismic activity, as well as the addition of trenhes and ridges along its shoreline.


 
Sources:
Key Concepts in Geomorphology
Climate Risk and Adaptation Country Profile
CentralAmerica.com
Earth 100 Million Years From Now
USGS Volcanic Map if Costa Rica

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