Cerro Negro
Cerro Negro is a very active, nascent composite cone, born in 1850. Its eruptions are part lava, part tephra, with lots of ash size tephra. Cerro Negro's basaltic lavas have water contents of up to 6%. These very high water contents make the eruptions very explosive, so the magmatic froth produced is highly fractured and shattered to tiny particles. Because basalts are hot, about 1200C, they are very fluid (low viscosity), which allows gas to segregate from the magma easuly. This allows simultaneous gas-rich explosions in the central vent and gas-poor lava effusions on the flank. The model of composite volcanoes that has alternating layers of tephra and lava, seems appropriate for Cerro Negro, although it is only an infant.
Cerro Negro's eruptions commonly occur in clusters that coincide with tectonic earthquakes. The current eruption sequence began in 1992, a few month prior to a major, tsunamigenic earthquake, immediately offshore from the volcano. The previous eruption cluster, 1968-1971 preceeded the Managua Earthquake of 1972, a shallow, strike-slip earthquake that destroyed the downtown of Nicaragua's capital. The initial eruptions of Cerro Negro coincided with a great Nicaraguan earthquake in 1850.
Cerro Negro appears to be a sensitive strain meter.
Cerro Negro Notes for Margins
Trip
Getting to Cerro
Negro and Las Pilas from the Motel Europa in Leon.
The area around Cerro Negro is scrub with numerous woodcutters’ trails. Thus, there are about a thousand and one paths to Cerro Negro. The notes below have served me well since I got them from Bill Rose sometime around 1973. The notes were the result of frequent wrong turns. If your jeep has no functioning odometer (35% chance), good luck!
I recommend staying in Leon the night before and departing for the volcano at the crack of dawn. It is very hot and Cerro Negro is black, so an early and cool start is the best way to visit. Also, the Europa is a nice place. You will enjoy negotiating your overstuffed pack up the stairs. With luck you will experience many fireworks, but at least the train is gone. Sometimes the hotel has food, sometimes not, but there is a fine café on the corner of the main square opposite the NE corner of the cathedral. There is also a supermercado nearby for lunch fixings. Many gas stations have large (5 gal I think) bottles of Salvavidas (pure water). Strap one of these in your jeep before heading out. The bottle deposit is a bit steep but the water is cheap.
The first step (below) is finding the large unpaved road that heads in the general direction of Cerro Negro. Do this the evening before so you can find it at dawn. Try to be the last vehicle into the parqueo of the hotel, so you can exit cleanly in the madrugada.
Go east (right) on the road in front of Hotel Europa until you get to the major paved road.
From there it is 0.35 km to the left (north) to where the large unpaved road appears on the right. All further mileages are noted from this right hand turn.
0.0 km Turn east off main road onto dirt road.
6.6 A major intersection, go straight.
7.8 Turn right.
8.2 Turn left.
8.3 White house (first aid or medical station) on left
(NOTE by 1993 no longer white, closer to black)
8.3 con’t. Don't take the right turn.
9.0 Take left.
10.7 A small village.
11.3 Take left fork.
11.7 Take right fork.
11.9 Don’t take left.
14.5 Don't take left and slightly farther, don’t take right.
15.15 Take left fork.
18.15 Take left fork.
18.6 Take right fork.
19.8 Here you are coming in off the branch of a fork, when returning be sure to take the LEFT fork.
21.6 At fork take left for 1 km to get to Cerro Negro. From this point the road improves because the Municipality of Leon has widened and improved the former jeep track into a road. They also created between july 2000 and july 2001) a nice path across the lava flow at the base of Cerro Negro, making the climb easier but less wild.
NOTE: stop well before volcano, watch for large bomb craters that ruined the road.
Note the woodcutters path (a red-black scar) straight up one of the small cones making up the Las Pilas complex. This is a pleasant climb except for some sliding scoria. A good way into Las Pilas-El Hoyo. A great photo of Cerro Negro, especially with the low light angles at dawn.
I always climb Cerro Negro from the upwind direction but even there it is three steps forward, two steps back. Walk to the upwind side (SE) along the lava flows just at the base of the cone. This is easy except for the urge to sample the beautifully crystalline bombs and flow blocks. Lots of cumulates and shallow crustal xenoliths are available as well. This is a wonderful petrology lab, especially for pyroxeneophiles. The olivines are commonly honey brown, even when quite fresh. Volcanic gas at the summit causes alteration so the base is where to get a souvenir.
At the summit there are wonderful views but beware of stinging insects. The updraft as the trade winds rise over the cone lofts all manner of insects to the summit. Some may come voluntarily to drink the condensed steam. The gasses seem to anger the insects. I have been stung twice.
Beware the anteater. When I first saw an anteater at the summit of Cerro Negro, I thought he was the Einstein of anteaters, or the perhaps the Columbus (Colon). At the time I was shepherding a field course of Dartmouth students who decided to "save" the anteater. With great difficulty they got the beast to the base of the cone and fed it water. When we returned the next morning, he was back at the summit. Because Cerro Negro looked like the world’s largest anthill, I harbored romantic thoughts about a genius anteater or a dying anteater, who had found heaven on earth. Alas, Richard Harwood saw another anteater there two decades later and observed it busily eating all the disoriented insects. So Cerro Negro is just a snack bar and any anteaters there do not need to be "saved".
The descent can be as short as a few seconds. Go to where the scoria is fine and "ski" down in giant down bounds. If your knees are more like mine, just shuffle down in the comfortable solitude of your own personal landslide.