The horrible megatsunami, coming soon...

[MG1962]

That's about 112 cubic miles of rock.

Do you know how Day and Ward computed that total? I don't, but I wish I did. My napkin computations seem to say they took the entire volume of the bottom third of the island (all that is south of the caldera), both east and west, assuming a constant slope from shore to peak of the ridge, and counted right down to sea level. That seems like a pretty good landslide. Even smooth avalanches don't go that far.

I don't think that number is right 500 billion cubic meters = 500 million cubic kilometers = 310 million cubic miles......am I missing something

 

[MG1962]

Yes, I agree with that assessment. No one knew what had happened until the Dutch got the ship in the harbor out.

Except that it is wrong. After the second explosion most of the island was gone, the third explosion which created the biggest waves was caused by the sea rushing into the exposed magma chambers

 

[Marduk]

That's about 112 cubic miles of rock.
.

thats quite small compared to the liquid output of the Altai flood, which iirc was 10,000,000 m3/s,

 

[quarky]

Back on topic:

OMG! We are doomed, I tell you! Doomed!




Its time for "Duck and Cover" to make a come-back.
Maybe a new style, for the mega-tsunami?
Kiss your ass goodbye with a life-jacket strapped on firmly?

Those jackets won't be cheap to buy.
Protection from terrorists and drugs has pretty much bankrupted the schools.

Stupid mega-tsunami. I'm really mad at it. Pre-emptively annoyed.
My fear related energy is all tapped out. I just don't have emotional space for this wave.

 

[Checkmite]

I am not entirely sure your description of the eruption is all that accurate

The current scientific consensus about the destruction of the Krakatau volcano is that a large magma chamber below the island was emptied (or largely emptied) by the paroxysmal eruption, and the island above collapsed into the remaining void - i.e., the formation of a traditional caldera. The magma chamber's shape can even be roughly traced by the parts of the original island that were left after the collapse.

At any rate, the catastrophic collapse would have had the effect of a tremendous landslide of the type predicted in the "mega tsunami" show.

 

[Corsair 115]

Back on topic:

OMG! We are doomed, I tell you! Doomed!

Well, when the sun goes red giant, that's pretty much the end of the good ol' Earth (and whatever happens to be alive on it at that time).

 

[Pixel42]

TV Science can't all be dry, and as you say, Horizon programs do normally contain information. (The standard has fallen off recently; most things BBC have recently, but not Sir David Attenborough, may his tribe increase.)

Horizon definitely went through a bad patch at around the time this particular documentary was made, they really dumbed it down, but the last couple of series have been much better. There have also been some excellent science documentaries made for BBC4.

 

[MG1962]

The current scientific consensus about the destruction of the Krakatau volcano is that a large magma chamber below the island was emptied (or largely emptied) by the paroxysmal eruption, and the island above collapsed into the remaining void - i.e., the formation of a traditional caldera. The magma chamber's shape can even be roughly traced by the parts of the original island that were left after the collapse.

At any rate, the catastrophic collapse would have had the effect of a tremendous landslide of the type predicted in the "mega tsunami" show.

I think we are going to have to agree to disagree on that consensus you mention

 

[Checkmite]

What is your impression of the event? I'm curious, as I really don't see any other possible scenario.

 

[truethat]

I've seen the movie, it's not new and "coming out", it's been out more than 3 months, and for the record, your view on the bird flu is over-simplistic and naive.

But back to the topic.

LMFAO! Of course I am.

Back on topic:

OMG! We are doomed, I tell you! Doomed!




Its time for "Duck and Cover" to make a come-back.
Maybe a new style, for the mega-tsunami?
Kiss your ass goodbye with a life-jacket strapped on firmly?

Those jackets won't be cheap to buy.
Protection from terrorists and drugs has pretty much bankrupted the schools.

Stupid mega-tsunami. I'm really mad at it. Pre-emptively annoyed.
My fear related energy is all tapped out. I just don't have emotional space for this wave.

I don't see how so many of these supposed scientists can't see that they are absolutely no different than any of the Christian fundies predicting the end times over and over again. The signs are all there. THE SIGNS THE SIGNS!

The planet could get hit with a stray meteor and we'd all be done and over with. Yes there could be tsunami's, bird flu pandemics, a polar shift, major earthquakes, superstorms.

It's like the 1950s all over again, but instead of giant bugs we have other horror ideas.

All about fear mongering. It's stupid.

 

[Turgor]

I don't think that number is right 500 billion cubic meters = 500 million cubic kilometers = 310 million cubic miles......am I missing something

In case you didn't figure out what you were missing yet: 1 billion cubic meters = 1000 m by 1000 m by 1000 m = 1 km by 1 km by 1 km = 1 cubic kilometer. Same goes for conversion between cubic km and cubic miles, you can't just divide by the amount that works for a single dimension.

 

[Venom]

I don't think that number is right 500 billion cubic meters = 500 million cubic kilometers = 310 million cubic miles......am I missing something

In case you didn't figure out what you were missing yet: 1 billion cubic meters = 1000 m by 1000 m by 1000 m = 1 km by 1 km by 1 km = 1 cubic kilometer. Same goes for conversion between cubic km and cubic miles, you can't just divide by the amount that works for a single dimension.

Aw, why didn't we just Stundie him.

 

[Hellbound]

At any rate, the catastrophic collapse would have had the effect of a tremendous landslide of the type predicted in the "mega tsunami" show.

I'm not sure about this.

The show's prediction had a large mass falling into water. The scenario you described had a large mass falling into a void emptied of magma. If I understand correctly, the majority of the wave is caused by the infalling mass pushing the water down (the out as it's deflected by the sea floor). With it falling into an emptying magma chamber, it's not pushign on anything (or, less tuff anyway) because (presumably) the chamber is not full of water.

Course, IANAE, not liable for damages caused by acting on information contained in this post, may not be held responsible, etc, etc, etc,

 

[CapelDodger]

Horizon definitely went through a bad patch at around the time this particular documentary was made, they really dumbed it down, but the last couple of series have been much better. There have also been some excellent science documentaries made for BBC4.

Indeed, BBC4 has presented some first-rate science and history of science series. I particularly like Jim "Eat My Shorts" Al-Khalili.

 

[CapelDodger]

The show's prediction had a large mass falling into water. The scenario you described had a large mass falling into a void emptied of magma. If I understand correctly, the majority of the wave is caused by the infalling mass pushing the water down (the out as it's deflected by the sea floor). With it falling into an emptying magma chamber, it's not pushign on anything (or, less tuff anyway) because (presumably) the chamber is not full of water.

I think the major impact is from sea-water flooding into the void and flash-boiling. That would stir things up a bit.

 

[MattusMaximus]

Screw the megatsunami - it's the Zombie Apocalypse for me, all the way

 

[jhunter1163]

I am not entirely sure your description of the eruption is all that accurate

I have Simon Winchester's book regarding the Krakatau event. The Dutch were able to get telegraphic messages out within a couple of days of the event. And it was indeed devastating; it is believed that the culminating explosion was the loudest sound ever heard by human beings (it was heard almost three thousand miles away.)

 

[Checkmite]

I'm not sure about this.

The show's prediction had a large mass falling into water. The scenario you described had a large mass falling into a void emptied of magma. If I understand correctly, the majority of the wave is caused by the infalling mass pushing the water down (the out as it's deflected by the sea floor). With it falling into an emptying magma chamber, it's not pushign on anything (or, less tuff anyway) because (presumably) the chamber is not full of water.

Course, IANAE, not liable for damages caused by acting on information contained in this post, may not be held responsible, etc, etc, etc,

I see what you mean. However, there certainly was an incredibly large tsunami. The sibsidence of the island is rather self evident, but I suppose there's room for speculation as to the exact mechanism that led to the tsunami.

When I imagine this event in my mind, I see the (rather large) island breaking up and collapsing to form a caldera, and suddenly a very large area that was previously above sea level is now below sea level. It seems to me that the ocean compensates in the form of tremendous quantities of seawater - an extremely local mega tsunami if you will - rushing inwards to fill the empty space. Based on my (admittedly limited) understanding of fluid physics, I predict that this roughly ring-shaped wave would come together in roughly the center of the (now filled) space, perhaps building from momentum to a significant height at the focus, at which point the momentum would reflect outwards as a second large ring-shaped wave spreading away from the scene. Does this sound plausible to anyone?

 

[Correa Neto]

Here's something one must take in to account regarding caldera collapse-induced tsunamis- a ring usually remains above sea level. In some cases, there's a single access to the internal collapsed area. This may have an effect on how the wave propagates, creating a shadow zone.

This put, there's an extra source for tsunamis in huge eruptions- the collapse of the plume of hot gas and ashes. This may create a surge of pyroclastic flows which will cover the island's surroundings with a blanket of only the IPU knows how many cubic tons of material.

There are more than one way to generate tsunamis in volcanic eruptions... Earthquakes, pryroclastic surges, collapse of the mountain (inward and also outwards), phreatomagmatic explosions (water+magma= KABOOOM!). Staying around is not healthy.

 

[Checkmite]

Here's something one must take in to account regarding caldera collapse-induced tsunamis- a ring usually remains above sea level. In some cases, there's a single access to the internal collapsed area. This may have an effect on how the wave propagates, creating a shadow zone.

This put, there's an extra source for tsunamis in huge eruptions- the collapse of the plume of hot gas and ashes. This may create a surge of pyroclastic flows which will cover the island's surroundings with a blanket of only the IPU knows how many cubic tons of material.

There are more than one way to generate tsunamis in volcanic eruptions... Earthquakes, pryroclastic surges, collapse of the mountain (inward and also outwards), phreatomagmatic explosions (water+magma= KABOOOM!). Staying around is not healthy.

There were certainly some huge explosions associated with the 1883 eruption. It was heard in Australia and possibly as far west as Rodriguez Island off Madagascar.