La Brea: what if a giant abyss suddenly opened up?

While the series La Brea just beginning to be broadcast in France since November 2, 2022, in our new episode of Science, it turns, we look at its realism. Or at least the credibility of the trigger: is it possible for a giant sinkhole to suddenly open up in the middle of a city?

Since November 2, 2022, the series La Brea is scheduled on TF1 every Wednesday. Initially broadcast in 2021 outside France, it begins with the opening of a giant chasm in the middle of Los Angeles, in the United States. Many people then fall into this crater, while others try to understand what happened. We then learn — spoiler warning — that they have in fact been plunged into a parallel dimension: they are in the same place, but in 10,000 years BC. At the same time, prehistoric birds come out of the abyss and arrive in the present time, confirming the idea of ​​a dimension in the past. Many discoveries follow, on one side or the other, while the mysteries accumulate just as much. But how much realism is there in this science fiction series?

Giant sinkholes like in La Brea actually exist!

While time travel is of course absolutely implausible, the opening of a crater is! Called ” sinkholes “, these sinkholes are formed when the rock collapses under its own weight. This collapse occurs mainly for limestones, carbonate rocks easily soluble in water. When water seeps into these rocks underground, some of it dissolves, and depressions are then created as the water recedes. This then forms what are called karstic environments: geological structures resulting from the hydrochemical or hydraulic erosion of rocks, often caused by rainwater. We can notably cite the very famous Gouffre de Padirac, resulting from the collapse of the vault of an old natural cavity and a depth of 103 meters!

Such collapses often take on a circular shape, and although they sometimes occur slowly, the process is mostly very sudden. This is what happened in August 2022 in Chile, where a gigantic crater appeared! Hollows have built up in the rock, and the roof covering the hollows—or from our point of view, the floor—falls when its sustained weight exceeds the capacity of the rock to hold its ceiling in place; for example, if the water recedes. The depth will depend on the flows and the depth at which they cut into the rocks. Human activity can also influence, as when it contributes to pumping water quickly, by lowering the level of the water table.

In cities, the process is much more rarely observed and fortunately! The origin differs in these cases: the sinkholes come this time from artificial processes, such as the rupture of water pipes, the accumulation of construction, the excessive pumping of underground water or even mining. But, in general, cracks or slight subsidence occur before the disaster, making it possible to prevent it. Urban sinkholes also measure a few tens of meters in diameter on average, a size very far from that of La Brea! We can nevertheless cite the giant abyss that occurred in Montevallo, Alabama, in 1972: 91 meters wide, it appeared in a single night, engulfing trees and waking up the people living nearby!

La Brea: a real prehistoric place

Thus, a giant abyss is possible. But that wide, it’s impossible. On the other hand, some natural craters reach several thousand meters in depth, such as the Sarma cave located in the mountains of Abkhazia, Georgia, and reaching 1,830 meters in depth… making the crater of La Brea plausible on this point. As for the prehistoric animals from the crater in the series, they obviously seem improbable, but are not based only on fiction! Because the title of the series, La Brea, refers to an actual prehistoric site located in downtown Los Angeles: La Brea Tar Pits. More precisely, it is a deposit of fossils dating from the end of the upper Pleistocene, therefore between 40,000 years and 11,700 years before our era.

Thousands of animals found themselves trapped in a natural tar pit as they searched for water in times of drought. By plunging into the pool of asphalt, their bodies sank into this particularly viscous oil, unable to get out. A few centuries later, in our time, multiple excavations have taken place and have made it possible to find in particular a large quantity of fossils of insects and plants, but also larger specimens such as snakes, prehistoric horses, or even mammoths!

Today, the finds are housed in a large museum in the heart of Los Angeles, complete with a reconstruction of the place as it might have been 40,000 years ago. The idea of ​​the series is thus to take back these animals stuck in the well, but this time to imagine that it becomes a passage to the past, where the animals are not dead!

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