I heard once that the iceberg that sunk Titanic may have ‘turned turtle’ – that is, the underwater portion had melted to the point to where it became top-heavy and it rolled over. This would have given the iceberg a darkish blue translucent surface, as opposed to the bright white surface we normally think of when we envision an iceberg. Such an iceberg would be even harder to see on a moonless night on calm seas than a snowy white one.
However, a photo taken three days after the sinking shows a regular white iceberg. It is described as ‘perhaps the very one’ that Titanic struck.
I think I heard this factoid around the time the movie Titanic came out, and I haven’t heard it since. Aside from the 1912 photograph (which, as far as I know, has not been verified as being of the iceberg), is there any evidence one way or the other whether the iceberg was upright or upside-down?
Dunno about it being turned upside down, but the iceburg that was photographed was described as having a smear of red paint on its side. It was probably the culprit, unless there was another ship that struck an iceburg around the same time and in the same area.
Icebergs float because the density of ice is lower than that of seawater. No matter how much an iceberg melts, the ratio of those densities dictates that about seven-eighths of the iceberg will always be underwater, even if the iceberg would somehow flip over.
If the bottom becomes lighter than the top and it turns over, that means the bottom is melting faster than the top. Since the bottom is affected mostly by water, and the top by air, it seems logical to assume that the iceberg is now in warm water with cold air above (and it could snow or rain as well, increasing the weight on top). Either the weather changed or it drifted into that situation.
To reiterate what Musicat posted, they become top-heavy because of different melting rates of the ice in water and air.
Water is much more massive than air, and retains heat better. When I lived in SoCal I’d hear the surf report every morning. It was not infrequent that the water temperature was warmer than the air temperature. As a berg drifts northward (from Antarctica) or southward (from the Arctic), the water gets warmer. The water may be 1°C – and water conducts heat better than air – and it may still be freezing topside. So the submerged portion of the berg melts more quickly than the non-submerged portion. When enough of the submerged portion melts, the top becomes heavier than the bottom and the berg rolls. Or, as noted in the links, it may break up and the individual pieces will find their own buoyancy balances.
To simply sink down in the water without turning over the melting rates would have to be equal, or the top would have to melt more quickly than the bottom. Think of a rowboat that springs a leak on the bottom. As an analogy, this is like the top of an iceberg melting more quickly than the submerged part. It will sink down. But imagine a heavy man climbing to the top of the mast of a small sailboat (analogous to the submerged portion of the berg melting more quickly than the top). The boat will roll over.
From all that I’ve read, the lookouts didn’t see the iceberg in time, because:
(1) They weren’t issued binoculars.
(2) It was a dark, moonless night, and the wind was dead calm, so there were no waves breaking against the iceberg which would have allowed them to see it sooner.
(3) The lookouts were distracted by Leo DiCaprio and Kate Winslet running from the cargo hold, still hot & steamy from their recent passionate lovemaking. (However, whether that incident had any real impact on the disaster has never been determined.)
Since there’s more than enough verified reasons why the iceberg wasn’t seen in time, I don’t see any reason to speculate about other ones.
From what I’ve read about icebergs, since 90% of them is underwater, a ‘berg can be affected by two different currents at once, moving in two different directions. This is what makes towing them so difficult: not only are they freakin’ huge, but there’s a tremendous conflict between the below- and at-surface crosscurrents.
If those crosscurrents were even a few degrees different in temperature, it could cause uneven melt on one side of the iceberg only, changing its center of gravity. That’s why Johnny LA pointed out that they shift slowly, but may sometimes roll suddenly.
But as we know, the 1912 style Straight Dope Pit thread decided that the Titanic disaster was the fault of the evil Taft administration. Isn’t progress wonderful?
But wouldn’t this presume that the berg was somehow ‘balanced’ on the water? As Walloon mentioned why wouldn’t it gradually float lower as the bottom melted? I’m not suggesting they don’t turtle, just that might be another factor at work.
Yes, it is ‘balanced’ in the water. Let’s go back to the rowboat. You’re sitting right in the middle of it. The boat is on an even keel. Now you decide to sit on the starboard gunnel. The boat wil list to starboard since the CG has changed. Same thing with an iceberg. It will float in the water in whatever attitude is determined by the CG. Change the CG, and the attitude will change.
So you’ve go this iceberg that’s floating happily along. Only the submerged portion is melting at a faster rate than the portion that is in the air. The meltwater does not remain ‘attached’ to the iceberg, but mixes with the surrounding ocean. That is, it’s no longer part of the iceberg. So as the submerged part of the iceberg melts the CG changes. As this happens the iceberg will begin to tilt so that it is in equilibrium with its new CG. At some point the top may become heavier than the bottom and the iceberg will roll. This doesn’t mean that it will roll exactly 180º; it will roll until it finds its new balance.
Okay, here’s another analogy. You know those ‘drinking bird’ toys? The bird is upright as long as most of the liquid is in the bottom bowl. As the water makes its way to the head, the bird tips slowly at first. Then it reaches the critical point and tips over all at once.
Of course icebergs aren’t designed toys that will perform predictably. How much it tilts or rolls depends on the shape of the berg, sea conditions, atmospheric conditions, rate of melting, etc.
The link Walloon posted seems to indicate that the red paint iceberg was a separate one from the one that hit Titanic, and that the red paint iceberg is something of a mystery.
The icebergs I’ve seen (on TV – I’ve never seen one in person) are white. When they turn over (also recorded on video) the bottoms are translucent blue.
First let me say that I have no knowlege about icebergs nor am I debating this from a place of not believing you, I’m just having trouble picturing it.
Back to the rowboat. I understand the CG thing. But the boat unlike the iceberg doesn’t change size. But suppose it did. Suppose the boat have several removable sides. So i’m setting in my boat and it’s floating at freeboard X. Then I jettison the outside hull, now I am at freeboard X-3" (let’s say), next hull X-6" ond so on.
The point being as I take away from the area of displacement (like the melting iceberg) the boat will slowly ‘sink’ not flip over. Why would the iceberg behave differently?
