Idle speculatiion – Looking at the shape of the Caribbean I wondered whether or not there was any evidence for or against its extraterrestrial origin. Possibly it was formed during the same epoch as the mare on the Moon. We know what to look for as evidence for craters left by smaller meteors, chemical & physical changes, shocked rock extending deep into the ground, upturned strata around the rim etc. But something large enough to cause the Caribbean would involve orders of magnitude larger kinetic energy and the geophysics may be unknown.
Are you sure you’re asking about the oblong Caribbean and not the more circular Gulf of Mexico? Not that it matters, the answer is “nope” in either case.
Anyway, while there’s some dispute about the origin of the Caribbean, “meteor” isn’t it. There’s just disagreement about which kind of igneous type it originated as. It’s either plate tectonics or a mantle hotspot. Or more likely a combo of the two.
But definitely not the same time as the lunar maria. Around 3 billion or more years too late. Ocean basins get recycled on a shorter timeline than that.
To complicate matters, there is a giant meteor crater there: it’s the one that killed the dinosaurs.
But it’s not Caribbean-size big.
‘Only’ 180 km. But it’s on the Gulf side of the Yucatan, not the Caribbean.
Given the last supercontinent (Pangea) is thought to have broken up around ~300 million years ago, and the Caribbean is therefore younger, the two events would not appear to be related.
Now that that’s settled …
It’s interesting to imagine an alternate history where the semi-circular Gulf of Mexico *really is *a fairly recent impact basin. At least recent enough to have not yet been recycled by plate tectonics. Given this hypothetical …
Seems to me the energy of an impact large enough to have formed the Gulf would have pretty well moltenized the entire crust, evaporated much of the oceans, and pretty conclusively terminated the atmosphere and biosphere for eons after the impact. I speculate it’d be pretty much a total planetary reset.
Anybody care to speculate or Google on this idea? How energetic an impact would it have been and what would have been the near-term consequences? How much smaller would this impact have been than the putative one which formed the Moon?
Read for yourself: Traces of Catastrophe: A Handbook of Shock-Metamorphic Effects in Terrestrial Meteorite Impact Structures, Bevan French, Smithsonian Institution Department of Mineral Sciences.
Stranger
Cool. Thanks.
I recently learned all about the Gulf of Mexico’s origins and development. Here I’ll just say that, about 200 million years ago, the block (small plate) which contained today’s Yucatan Peninsula, northern Guatemala, and the Campeche Bank was firmly nestled against North Anerica, and rotated from its present position. “Austin, Texas” was right next to “Comitan, Chiapas (Mexico)”; three plates met around Key West, Florida, including this same block (north of the “Yucatan Peninsula”), and Africa; and there was another triple junction at “Guatemala City,” “Piedras Negras, Texas,” and Venezuela.
Continental rifting developed in the late Triassic, and then the block started to separate in the mid-Jurassic as an oceanic rift opened up. The block slid relatively southward (while gradually rotating), so there was also a transform fault system along its west edge (as other Mexican terranes arrived from the west, they were “mis-aligned” by this transform fault, along the Isthmus of Tehuantepec.
The process was over by about 130 million years ago, though the margins of the Gulf underwent later developments, e.g. the Sierra Madre Oriental (mountain chains from Monterrey through the Huasteca region of Mexico), which were part of the same Laramide Orogeny (40 to 70 mya) that created the Front Range of the Rocky Mountains.
A more general bit of advice to the OP: if you’re curious about the origins of a water body, first find a map which clearly shows the continental slopes. Don’t be misled by where coastlines happen to be right now. Generally, the shallow seas offshore are just part of the continents (for many purposes of analysis) – so the “real” shape of oceans and seas is rarely what you think it is.
(That’s one reason it took decades for the scientific community to agree with Wegener’s insights about continental drift – we didn’t have much data on ocean depths until the me-1950s, when Mary Tharp and others ran their expeditions and produced their maps).
The simplest way to describe the Caribbean’s origin is that North America separated from South America, and a bunch of stuff passed between them, moving west to east on the same big Pacific “conveyor belt” that brought exotic terranes like Point Reyes and Palos Verdes to attach to California.
(BTW, in the last few million years, that conveyor belt has finally started to wind down, as the East Pacific Rise spreading center disappears under the North American Plate. Local effects vary, and include the San Andreas transform fault system, and the brand-new spreading center in Mexico’s Gulf of California. The fact that a spreading center can disappear under a continental plate makes you realize that tectonics is working at different scales, more or less independently: the scale of plates which we’re familiar with, but then also a bigger scale, of whole “plate systems” with their own relative movement.)