Laguna de Apoyo Crater Lake
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In the center of the Nigaraguan Pacific coast, in the middle of the long volcanic chain which runs through the country from north to south, there is a wide and extended crater in the form of an inverted cone, and in the center of it is one of the most beautiful lagoons in Nicaragua: Laguna de Apoyo. From the viewpoint at Catarina, you get a spectacular panoramic view of Laguna de Apoyo and its surrounding Natural Reserve, Volcan Mombacho, the city of Grenada, and the coast of Lake Nicaragua.
Crater Lakes
A crater lake is a lake that forms in a volcanic crater, caldera, or maar. These lakes generally form by explosive excavation (crater lakes) or collapse (caldera lakes). Lakes can also fill impact craters, but these are not usually referred to as crater lakes except in a few isolated cases.
Incoming precipitation fills the depression to form a deepening lake, until equilibrium is reached between the rate of water coming in and the rate of water loss due to evaporation, subsurface drainage, and possibly also surface outflow if the lake fills the crater up to the lowest point on its rim. Crater lakes covering active (fumarolic) volcanic vents are often known as volcanic lakes, and the water within them is typically acidic, saturated with volcanic gases, and cloudy with a strong greenish color. Lakes located in dormant or extinct volcanoes (like Apoyo) tend to have fresh water, and the water clarity in such lakes is often exceptional due to the lack of inflowing streams and sediment.
Crater lakes can only stably exist when the water influx = water outflux. Precipitation rate, catchment area and any surface inflows, together with evaporation, subsurface leakage and surface outflows, all determine a lake’s survival potential in terms of maintaining water balance. Due to their unstable environment, some crater lakes exist only intermittently. Caldera lakes, in contrast, can be quite large and very long-lasting.
While many crater lakes are picturesque, they can also be deadly due to gas discharges and/or destructive lahars (hot mudflows composed of pyroclastic material and water).
Laguna de Apoyo
The crater of Apoyo was formed approximately 23,000 years ago after a strong volcanic explosion which left a hole measuring 6 km in diameter. As time passed, subterranean waters and rain filled the crater and the slopes became covered by vegetation. The volcano still has some underwater thermal vents and experiences the occasional seismic tremor, but for the most part, it’s considered dormant. (An earthquake in 2000 originated under the town of Catarina (which sits atop the western lip of the crater) and actually caused the water of the lake to slosh from side to side, starting a rumor (false) that it was boiling.)
Laguna de Apoyo has a surface of 48 square kms. It is very deep: the lowest level of the conic hole is 100 m underneath the sea level and the shore of the lagoon is 75 m above sea level, making it the lowest point in all of Central America. Even though its water is not fit for direct human consumption, it is the most crystal-clear fresh water body in Nicaragua, and possibly in Central America, having a low level of natural and human contamination. The temperature of the superficial water ranges from 27C to 28C. During summer months, as a result of the winds that strongly blow during this period of year, bringing cooler waters from the deep, the temperature gets slightly lower. Divers may occasionally encounter a warm thermocline over a subsurface thermal vent.
Apoyo Lagoon Natural Reserve
Apoyo Lagoon Natural Reserve is located between the departments of Masaya and Grenada in Nicaragua.
There are 2 main access points to get to the center of the Reserve (lagoon) that are accessible by car. One is located in the town of Catarina, and this can be reached through 3 different roads: one located along the Masaya-Grenada highway, another from the Masaya-Catarina road, and the last one from Catarina itself. The second entrance is located in Diria, at the viewpoint. Public buses are available from Grenada, but they require transfers.
Flora & Fauna
The reserve houses a tropical dry ecosystem. The flora consists of numerous species of plants and tropical dry trees, such as pochote, black rosewood, mahogany, marmalade plum and guacuco, as well as a large variety and amount of orchids. The fauna consists of mammals such as opossums, giant anteaters, pacas, jaguarundis, Howler and White-faced Capuchin monkeys, as well as a variety of reptiles such as green iguanas and common boas. Birds in the reserve are abundant, with oropendolas, falcons, hummingbirds, and nearly 65 species of migratory birds.
Laguna de Apoyo also contains a variety of fish species, including 4 species of mojarras (e.g., Arrow Mojarra (Amphilophus zaliosus)) which are found nowhere else – products of the forces of evolution in an isolated habitat.
Challenges Facing Laguna de Apoyo
Laguna de Apoyo has no superficial exits for its waters. This fact makes the lagoon and its ecosystem very weak and subject to harm.
A failed project to commercialize the production of Tilapias (fish) in the lagoon resulted in the release of this foreign species into a closed ecosystem. There are several possible negative consequences due to damage to the natural habitat that Tilapia causes when voraciously consuming algae.
The use of motorboats introduces hydrocarbons into the lagoon, which contaminates the water. Due to the missing public service of collecting black and grey water, most septic tanks are leaking into the lagoon. As well, deforestation and construction in the area have resulted in soil deposition into the lagoon due to the elimination of the natural filtration.
The lagoon has a relatively high amount of salt, but is still drinkable (even though not recommended for domestic use). The salt level has risen significantly over the last 20 years, and for 15 years the water level has been lowering at a rate of ~0.3m per year.
To claim this EarthCache you must
1. Take and post a picture of you and your GPSr at the posted coordinates with Laguna de Apoyo in the background and e-mail me the answers to the following questions:
2. What major factor accounts for Laguna de Apoyo’s fragile ecosystem and threatens its future viability?
3. Laguna de Apoyo has very steep slopes surrounding its shores, which are at 75m above sea level. From the posted coordinates, take an elevation reading on your GPSr and estimate the maximum height of the slopes below you.
Do NOT post your answers, encrypted or otherwise, on your log.
DO NOT LOG AS A FIND UNTIL YOU HAVE A PICTURE READY TO POST AT THE TIME OF LOGGING A FIND FOR THIS EC. Logs with no photo of the actual cacher logging the find or failure to answer required questions through e-mail will result in a log deletion without notice. Exceptions will be considered if you contact me first.
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