Blog Post #3

The predominant scale used for climate is Köeppen’s general scheme, which classifies specific climates using three groups of lettering. The west side of Costa Rica on the Pacific Ocean is considered an Aw climate. This includes a dry winter season with little sun. The east side is an Af tropical rainforest climate, typical for rain throughout the year. 

A map of the the various climates around the world according to the Köeppen scale. The first letter identifies the major climate type. The first letter identifies the major climate type. The second letter identifies climate precipitation. Lastly, the third letter refers to the climates temperature. Costa Rica (located shortly above South America and 10-11〫above the equator) is classified first by an “A” (tropical humid), and then the climate is further specified on each side of the country. The area of Cedral (close to San Jose) holds the world record for the amount of rainy days at one site (359 days in 1968). In general, the Af climate type will receive the most rain throughout the year and is typical of the east side of Costa Rica.

One of the major wind patterns that affect Costa Rica are the north easterly trade winds. These winds are caused by heavy cold air coming from the northern hemisphere of the earth. As the winds get closer to the equator, they collect warm air and flow upward (northeast) from the Caribbean to the Pacific side. The warm air is caused by solar radiation hitting regions on the equator. These winds attempt to balance air pressure throughout the earth and follow a pattern determined by the Coriolis Effect. The Coriolis Effect is caused by the Earth’s rotation. As the Earth spins, the winds are deflected away from the equator and start to “curve”. 

The above picture shows the north-easterly trade wind patterns that flow over Costa Rica, which help carry moisture in the form of mist to the Tilaran mountain range throughout the country. The video shows the Coriolis effect, which causes these winds to deflect from the equator based on earths rotation. 

Due to the wind patterns, moisture in the form of mist become a “cloud forest” once reaching the mountains in central Costa Rica. This is one way that the country receives its vast amount of precipitation, along with other rain clouds that are transported by the wind patterns. 

A picture of a “cloud forest”, caused by the east-traderly winds. The moisture from the Caribbean waters is transported in a mist form, and settles as clouds as it moves to the central part of the country in the mountains rainforest region.

The climate in Costa Rica is identified by two major seasons: summer (dry) and winter (wet). On the Caribbean slope, the rainy season begins from April-December. The wettest months are from July-November.  The rainy season on the Pacific slope is from May-November. During this time, the north-easterly trade winds are reduced in intensity. As a result, storms come in from the Pacific Ocean from September-October. In the northern part of the Pacific slope, sometimes no rainfall occurs for several months.

This map shows the average precipitation each year in Costa Rica. The eastern side of the country experiences more rainfall than West, making it more so of an Af tropical rainforest climate. 

Works Cited:

http://www.anywherecostarica.com/maps/weather

http://www.nicoyapeninsula.com/weather.php

http://kitecostarica.net/costa-rica-wind-forecasts/

http://journeys4good.com/blog/volunteer-travel/volunteer-teaching-in-costa-rica-the-cloud-forest-school/

http://www.worldheadquarters.com/cr/climate/

Blog Post #2

On November 4th, 2010 the San Antonio de Escazu suburban region of Costa Rica was impacted by a mudslide. This populated city is surrounded by many steep mountain and volcano slopes, which are prone to events of mass wasting (downward movement of rock and sediment that transports materials). Mudflows can be very damaging, as they destroy and bury whatever is in their path. The mudslide of 2010 had lots of water in the flow due to heavy rains, and it was very destructive as the fast stream that did not give residents time to prepare.  23 people died trying to escape the flow and several homes were buried. 

A picture of a house caught in the middle of the 2010 mudslide. The power of the mudslide has destroyed the house, and will integrate its remains into the stream as it moves material further down the slope. After the mudslide stops as the water seeps out of the sediments, the bonds will restrengthen as the mud solidifies, and the house will be buried underneath a solid material. (Photo credit: srnnews.townhall.com)

This mudslide was offset by heavy rains in the area, which loosens the bonds holding the soil and sediment together. The loose ground then forms a thick muddy fluid that quickly flows down the slope and solidifies after the water stops flowing through. 

Excess water from heavy rains mixes with soil and flows downhill in the pictured mudslide from 2010. Since the flow had so much water, it moves very fast has the power to destroy what is in its path as the telephone pole is destroyed. This picture also shows that mudslides accumulate material such as branches, plants, and any rocks and moves this material downslope with the flow. (Photo credit: www.welovecostarica.com)

The soil composition and structure in Costa Rica was the “perfect recipe” for a mudslide to occur. Based on a study, the main soil types consist of loam, sandy loam and silty loam, which create a porous soil. This soil is less flocculant (particles that stick together) than others, which means that it is more prone to water particles slipping between soil particles.

Soil Ternary chart showing the different types of soil compositions. Since Costa Rica consists of mainly sandy loam, medium loam, and silty loam. All consist of little clay and more silt, with varying levels of sand. Clay is the most flocculant, and sand is the least, so this chart shows that Costa Rica’s soil composition is porous. Photo Credit: Oneplan.org

The layers of soil in Costa Rica have a thick O horizon, which is the organic matter consisting of decaying material (leaves, dead animals, ext.). There is also a thick A horizon, which is dark in color from the nutrients and supports plant growth. The B horizon consists of minerals that have trickled down from the O and A horizons. These minerals have been compressed in a blocky form, which are clusters of soil that allow water infiltration. 

The soil horizons are shown. Photo Credit: llrs.co.nz

A soil profile taken from the Charles Schembre study. You can see the many horizons as discussed above. The top O horizon is where you can see vegetation, and the dark soil underneath is the Topsoil. Below these, the lighter colored soil is the B horizon. If you were to keep digging, you would also be able to see the C and R horizons. 

Blog Post #1

In this blog post, we will explore the plate boundaries around Costa Rica, and the volcanism that is formed from these boundaries. We will also discuss the mechanisms of one of Costa Rica’s most recognized volcanos.   

Both of these images below show the Cocos oceanic plate subducting under the Caribbean continental plate. Due to this subduction, the northern part of Costa Rica will experience active volcanoes.

Plate Tectonic Movement Visualizations, Compiled by Jeff Crabaugh and John McDaris (SERC). 

Map by Geology.com and MapResources 

Red lines are plate boundaries, responsible for volcanism. Arrows show generalized directions of plate movement.

There are over 200 volcanic formations in Costa Rica among three volcanic ranges. They are the Guanacaste, Central Volcanic Range and the Talamanca. This map shows the location of the most recognized peaks, including the famous Arenal Volcano in northcentral Costa Rica (in the Guanacaste Range). 

Line A-B marks the location of the plate tectonics cross-section shown below.Map by Geology.com and MapResources.

Arenal Volcano:

Image © iStockphoto / M. Gabrenya. 

Arenal Volcano is a conical stratovolcano (tall and symetrical, formed by “layers” of past eruptions) that stands on the shore of Lake Arenal in northcentral Costa Rica. This volcano is formed by a convergent boundary, as the oceanic crust subducts underneath the continental crust, melting rock into magma. 

It is the youngest and most active volcano in the country, and has been in near-constant eruption for 7,000 years. This volcano is very explosive when it erupts, as composite volcanos are a mix of felsic and mafic rock composition. This means the flow of lava will consist of andesite, which is moderately viscous and known for large eruptions. In the eruption of 1968, 3 surrounding villages were burried and 87 people died. This eruption consisted of a pyroclastic flow (fast and dangerous ground-hugging flow of ash and rocks) and spewed out a huge ash cloud. Ash is composed of tiny rocks called Tephra which are especially dangerous to be around; when inhaled, it is harmful to human health. Sometimes ash clouds like the one from 1986 (pictured below) can blow deposits hundreds of miles away from the site of the volcano.

Resources:

http://traveltips.usatoday.com/many-volcanoes-there-costa-rica-100297.html

http://www.arenal.net/arenal-volcano-overview.htm

http://geology.com/volcanoes/arenal/

http://volcanoes.usgs.gov/images/pglossary/PyroFlow.php

http://capone.mtsu.edu/mabolins/final3.jpg

Welcome

Hello, we are Jeannette and Monique and we will be discussing the physical geography of Costa Rica. We chose this location because of its vast physical geography, which includes mountains, beaches, rainforests and plains. You will also find a mix of urban and rural areas intertwined with a large agricultural areas.