At https://eos.org/features/the-unsolved-mystery-of-the-earth-blobs/ … sent in by William, the subject being the hot mantle below the crust which appears to harbour two blobs the length of continents. They are at the foot of the mantle – above the molten outer core. The blobs are made of rock as in the rest of the mantle but they are heavier or denser than the surrounding mantle. They were discovered by seismic tomography. Seismic waves travel more slowly through the blobs – suggesting they are dense. There is little doubt the blobs exist yet nobody knows what they are. Twice a day Earth's crust rises and falls with the tides. The solid Earth experiences the same forces as our oceans. As the Sun and Moon pull on Earth the entire planet flexes and stretches …
At https://phys.org/print470377372.html … NASA study reproduces the origins of life on the sea floor – in a laboratory. The theory is that life on Earth first formed around hydrothermal vents. These are found around cracks on the sea floor.