Hurricane Harvey is set to be one of the costliest natural disasters in American history. It was both unusually wet and extremely slow, and as a result, it dumped a whopping 125 trillion liters (33 trillion gallons) of rain on the US, mostly on Texas – more than four times that unleashed by 2005’s Katrina.
Last week, geoscientist Chris Milliner of NASA’S Jet Propulsion Laboratory (JPL) sent out a tweet that contained a rather startling map. As various GPS markers across Houston have revealed, the city actually sank a little as Harvey dumped all of its precipitation on the unfortunate city.
Of course, a lot of the metropolis was underwater, but this isn’t quite what we mean here. There was actually so much rainfall that the Earth’s crust itself was depressed by around two centimeters (about 0.8 inches) for a few days. That may not sound like much until you remember that warping the surface of the planet isn’t actually easy.
A simple calculation by The Atlantic suggests around 125 gigatonnes (275 trillion pounds) of water fell from the sky back then. That’s a difficult number to envisage, so let’s just say that the water weighed the same as 155,342 Golden Gate Bridges. It’s about the same as 77 percent of the total estimated mass of Mount Everest.
Mount Everest, by the way, cannot get much taller. If it did, the crust beneath it would begin to sink in response. So it’s safe to say that a veritable mountain of water landing mostly on Houston had the same effect, except in this case, the land was forced downwards.
Someone asked Milliner if the GPS reading was simply due to the compaction of unconsolidated, sandy soil that was simply sinking under the weight of the water. Not so, says the scientist: The “subsidence is beyond noise level.” Although some soil compaction may be a factor here, if the ground rebounds and moves upwards again as the waters recede that will confirm the crustal warping theory.
Another person asked Milliner about climate change. As we’ve previously reported here, climate change doesn’t “cause” hurricanes, but it certainly makes them wetter and more powerful. Thus, it’s safe to say that Harvey’s record-breaking rainfall was worse than it should have been.
In response to the query, Milliner says: “Unfortunately, [climate change] is very real. You don’t have to believe politicians, just look at the data and science.”