Field Trip: Nicaragua
J-Term, January 2014
Over J-Term, St. Norbert College Geology faculty took 14 earth science students to Nicaragua for a 17 day field trip. Students spent the majority of their time on the mainland studying the geology, ecology, and culture of Nicaragua including several active volcanoes, tropical dry forests, cloud forests, and Lake Nicaragua. The last part of the trip was spent on the Corn Islands in the Caribbean studying coastal processes and reef ecology. The trip was a perfect opportunity for students to study geology outside of the United States!
Las Huellas de Acahualinca
Approximately 2,000 year old human footprints are preserved near the southern shore of Lake Managua. For footprints to be preserved specific conditions are required. The material has to be moist, and then the prints have to be covered quickly, in this instance by ash from a volcanic eruption.
Laguna de Tiscapa
Laguna de Tiscapa is a crater lake of an extinct volcano. This site is the beginning of the Tiscapa fault that runs through Managua. Movement along the Tiscapa fault caused the 1972 earthquake that leveled Managua.
Volcán Masaya is a caldera composed of 5 craters. It last erupted in May 2013 and is considered one of the most active volcanoes in the Americas. The steam in the photo is degassing from the magma chamber.
Las Isletas de Granada
We took a boat tour of Las Isletas de Granada. Las Isletas de Granada consist of 366 islands on Lake Nicaragua formed from a debris flow from Volcán Mombacho. The islands are composed of large chunks of basalt from the flow. We saw a variety of birds and had the chance to feed monkeys on one of the islands!
At Playa Granada, students examined the beach sediments to determine the composition and texture while Dr. McKean discussed the differences between the origins of what we saw on the boat tour and on the beach.
Reserva Natural de Volcán Mombacho
After 30 minutes of driving up the steep slopes of Volcán Mombacho, we were able to hike through a cloud forest (top right). The hike provided spectacular views overlooking the surrounding area. We were able to see the islands we had toured that morning (bottom right) and the smoking crater of Volcán Masaya off in the distance. Other neat features we saw were a fumarole (bottom left) and a fissure crack.
El Hormigon Outcrop
We came across this spectacular outcrop providing us with a view of the inside of a cinder cone! The layers from various eruptions are easily visible, as is the central vent.
A couple of days were spent on Ometepe Island, an island composed of two stratovolcanoes, Concepción and Maderas, in Lake Nicaragua. Concepción is active and Maderas is dormant.
Punta Jesús María
Punta Jesús María is a sand spit, which is a long bar of sand connected to land on one end. A sand spit forms due to longshore current when winds come in at an angle bringing sediment on shore. Over time, sand will build up forming the long bar.
After sketching the outcrop, students approached it to get an idea of what was going on (middle). Dr. Flood (left) explained that this site could have formed from ash fall or from a lahar/debris flow. It is most likely a combination of the two. Throughout the trip, students kept a field book with everything they learned (right).
The Apoya Caldera is a crater lake formed by a plinian eruption over 20,000 years ago. A crater lake generally forms from a collapse or a blast from an eruption. Today the volcano is dormant.
Las Ruinas de León Viejo – Puerto Momotombo
León Viejo was the original location for the city of León, but is now the city of Puerto Momotombo. León was relocated to its present location after an eruption in 1610 that scared people away. León Viejo was gradually buried by ash from Volcán Momotombo and is now being slowly excavated. The stratovolcano sits on the shores of Lake Managua. The picture is of the geology professors at León Viejo with Momotombo in the background.
San Jacinto-Tizate is a geothermal energy plant that produces 17% of Nicaragua’s energy. The plant is located in the vicinity of several young active volcanoes. A couple of the scientists at the plant gave us a presentation on the history and geologic setting of the plant. They took us on a tour of the inside of the plant and to various areas outside. We saw fumaroles, a mud pot, and rhyolitic resurgent domes.
Volcán Cerro Negro
Cerro Negro is a cinder cone but has some of the same characteristics of a stratovolcano. There have been 21 eruptions since 1850, meaning it erupts about every 8 years. We hiked up to the summit, where we saw what we thought was the central vent of the cinder cone (bottom right).
Juan Venado Wildlife Refuge
Juan Venado Island is a barrier island off the coast of Las Peñitas. A mangrove forest sits on the edge of the island. We took a boat tour of the estuary where we saw a variety of birds and a mangrove tree that was older than 80 years (upper right)! On the island there were numerous live sand dollars all along the beach (lower left)! Throughout the trip some of the students collected samples of sand, clay and volcanic rocks for research projects back at school. Here, Bailey Anderson ’16 collects sand samples for her senior thesis project (bottom right).
Volcán Telica is an active stratovolcano just over a kilometer high. We hiked up to the crater just in time to watch the sun set.
Mina La India
Students got the opportunity to visit the artisan mines of Mina La India to see how gold is extracted using colonial techniques. They put ground rock into a cow horn and add water to separate the gold from the rest of the sediment (top right and bottom left). Students used a hand lens to see gold particles within uncrushed rock samples (upper left and bottom right).
The last few days of the trip were spent on the Corn Islands (Great Corn and Little Corn). The islands sit on the Caribbean continental shelf and formed from rifting in the back arc of the subduction zone. Most of the time was spent on Little Corn studying coastal geology. We came across pillow basalts which are unusual at the surface, since they form on the sea floor. Sea level must have been higher when they formed (Miocene/Pliocene).
Little Corn Island
We snorkeled in the back reef of the coral reef on Little Corn. The back reef is located in between the shoreline and reef crest (where the waves break). There is low wave energy and high sunlight. The coral occurs in patches, because there is a low amount of nutrients and too much sediment. Snorkelers and pollution (sewage) are threatening today’s coral reefs.
After two and a half weeks of warm, sunny weather, it was time for faculty and students to return to Wisconsin for a couple more months of winter. Students were able to travel to various regions of Nicaragua learning all about the geology and ecology. The trip was also a great opportunity for students to experience a culture completely different from their own.