We usually think that the asteroid impact was the cause of the extinction of the dinosaurs, but now it seems that there may be more than one cause of the extinction.
At the end of the Cretaceous period, 66 million years ago, as many as 75% of all species on Earth, including dinosaurs, were wiped out. There is evidence that the culprit is an asteroid impact. The impact site was also found, in Chicxulub, Mexico. Of course, it’s not that the asteroid hit the dinosaurs directly, but that the impact created a dust that pervaded the globe; as the dust blocked the sunlight, the climate cooled dramatically, and the resulting ecological catastrophe led to the extinction of the dinosaurs.
But as the saying goes, “Misfortunes don’t come singly.” Scientists have found that the extinction event occurred almost at the same time as the violent volcanic eruption. These volcanic activities led to the formation of a type of rock known as “deccan basalt” in western India.
It would be fine if all this volcanic activity happened after the impact, which would have caused more geological activity, of course. But two groups of researchers in the US recently calculated the age of Deccan basalts and found that the Deccan eruption started 400,000 years before the extinction event and continued intermittently for about a million years — and, of course, asteroid strikes The outbursts became more violent and more frequent after that.
This means that the environment in which the dinosaurs lived had deteriorated long before the asteroid hit. Therefore, the intensified volcanic activity can be seen as another cause of the extinction of the dinosaurs.
Children appear to be well-protected during this outbreak. Most children have no symptoms or have very mild symptoms when they contract the virus. But because of this, the long-term effects of Covid-19 on children are sorely overlooked.
Now, there is growing evidence that a large number of children (with or without symptoms) have been infected with the virus for months, although the virus has been cleared, but still have many sequelae, including fatigue, muscle and joint pain, headache, Insomnia, palpitations, respiratory problems, gastrointestinal problems, etc.
For example, there were reports of a 14-year-old girl in the UK contracting Covid-19 in March 2020. After healing, she became sluggish and weak. After three weeks in bed, one day she made some gentle movements in the garden and soon felt heartache and had to lie back in bed. For the next 5 months, she spent almost all of her time in bed. Her symptoms come and go. When she felt better, her family took her out for a picnic, but each outing triggered a prolonged recurrence of symptoms.
Another British parent has five children. They were all infected with the virus in the early stages of the epidemic, and they all left behind sequelae. Nearly a year after the infection, her 4-year-old still has neck pain, lethargy, stomach problems and headaches. Her 10-year-old son also suffered from fatigue, stomach problems and pain around the heart.
The proportion of children with sequelae is still quite high. More than half of children aged 6-16 who have been infected with the new coronavirus have at least one symptom that persists for more than 120 days.
Of course, it does not rule out the possibility that these symptoms will gradually decrease over time until they disappear.
When you think of deserts, the first thing that probably comes to your mind is sand dunes. They vary in size, roll up and down, and take on ever-changing shapes under the strong wind.
Dunes are not only found in deserts, but can also form underwater and even on other planets. For example, on Titan, the only planet in the solar system other than Earth that has a liquid lake on its surface (the lake water is liquid methane), there are large tracts of unspoiled sand dunes. “Sand” is actually particles of solid hydrocarbons.
Dunes are known to migrate. We know from aerial photos that the sand dunes in the Sahara Desert can move more than 100 meters a year.
Thus, a mystery arises: Since the dunes are always moving, they should collide frequently. When they collide, they either exchange materials and eventually all the dunes become the same size; or they merge to form larger and larger dunes. Why didn’t either of these things happen?
This mystery has existed for a long time. Part of the reason is that, after all, the dunes are moving too slowly, and the conditions in the desert are so harsh that scientists can’t stand there all year round.
But the mystery was finally solved recently. Scientists at the University of Cambridge, UK, used water instead of wind to conduct experiments in water tanks. They pump water into the dunes underwater to simulate the effect of wind on the dunes. Although one is wind and the other is water, the basic principle is the same as that of sand dunes. The force of water is stronger than that of wind, so it can speed up the movement of the dunes.
The team found that when the front dune was moving, the next dune was also moving, so the dunes did not actually collide. If it is restored to a realistic scene, it is like this: when the wind blows to the front of a dune, then a turbulent vortex will be generated on the leeward side; this vortex will continue to roll the sand of the latter dune to the back, so the overall effect Yes, the front dune is moving back, and the back dune is also moving back. This explains why the dunes don’t merge.