[Frantzie]

Well here is my question again and a freeper posted - the width:

“about 34 miles by 45 miles, according to WikiPedia.”

Big Volcanos like the scary ba*tard that is baby Krakatoa building up in the S Pacfic usually build up into a mountain overtime. The beast in the S Paficif grew from the seabed growing and growing.

At the top or the opening (foget the technical term again - cone??) It fairly narrow. The pressure builds and eventually blows.

Now a caldera is sunken in and really wide. Do scientist have any way of know if it was a caldera when it blew??

If it is 34 by 45 miles across can the pressure be relieved so it may never blow with the same force? Any geologists here?

[ETL]

Now a caldera is sunken in and really wide. Do scientists have any way of knowing if it was a caldera when it blew??

I believe there WAS a mountain there before the last super eruption. If you look at the topography in that region (the hot spot trail) you'll see that a whole lot of mountains have been blown away by past eruptions. The browns and tans are existing mountains.

Figure 1. Path of the Yellowstone hotspot. Yellow and orange ovals show volcanic centers where the hotspot produced one or more caldera eruptions- essentially "ancient Yellowstones"- during the time periods indicated. As North America drifted southwest over the hotspot, the volcanism progressed northeast, beginning in northern Nevada and southeast Oregon 16.5 million years ago and reaching Yellowstone National Park 2 million years ago. A bow-wave or parabola-shaped zone of mountains (browns and tans) and earthquakes (red dots) surrounds the low elevations (greens) of the seismically quiet Snake River Plain. The greater Yellowstone "geoecosystem" is outlined in blue. Faults are in black.

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[Steve Van Doorn]

Krakatau Caldera was about 7-km-wide (over 4 miles)

[ETL]

Now a caldera is sunken in and really wide. Do scientists have any way of knowing if it was a caldera when it blew??

These types of volcanoes don't really form the familiar cone-shaped structures. They tend to blow all at once in a very violent explosion. If a mountain happens to be above it at the time it blows, goodbye mountain! The Northern American plate slowly moves over the source of the volcanism (a volcanic "hot spot"), carrying the land surface with it.