Wednesday, April 22, 2009

Pantasma "Crater"

In studying the geology and archaeology of Nicaragua, I noticed a prominent landmark north of the city of Jinotega in the central highlands of northern Nicaragua. It is visible as a circular structure in the middle of the Google Earth image below.

In the image below, I have circled the crater in yellow.

If you study the topography, it is clear that this is a well defined circular depression. I found that it is named "Pantasma" after a village located within the crater. Googling it, I found that there are websites that suggest this may be an impact crater. The Wikipedia article on Pantasma describes this theory. I think impact craters are pretty interesting, particularly because I worked in and around the Chicxulub Crater in Yucatán.

Unfortunately, I feel impelled to point out that Weyl's authoritative tome Geology of Central America (1980: Figure 107) maps this as a caldera, one of several responsible for the Mio-Pliocene out-pouring of ignimbrite sheets that blanket the region. The statement that appears in the Wikipedia is not well-supported by the evidence and probably should be removed. The Pantasma area must have been a smoking hell when all these giant pyroclastic flows were emplaced. The Río Estelí runs through this region a bit further west. The name Estelí is said to derive from the Nahua word for obsidian, itzli. I wonder whether there actually is obsidian in the area or whether some of the glassy ignimbrite merely recalls obsidian.

Reference cited

Weyl, Richard (1980). Geology of Central America, Second edition. Berlin: Gebrüder Borntraeger.

No comments:

Post a Comment