#earths-core

#earths-core

Our new study suggests that the Apollo samples are biased to extremely rare events that lasted a few thousand years - but up to now, these have been interpreted as representing 0.5 billion years of lunar history. It now seems that a sampling bias prevented us from realizing how short and rare these strong magnetism events were.

Although Kansas has no active volcanoes, the region marks the southern reach of the Midcontinent Rift System, a massive tectonic event that nearly split North America apart in Earth's distant past. When magma forced its way through the crust during that period, it left behind hardened igneous rock and deep fractures that remain buried thousands of feet underground.

Land is one of those things that can disappear even as you see it. It falls away beneath you, becoming merely the ground under your feet, because you're thinking about where you're going, or a place slowly blurring out of focus from the airplane window. Land is a primal word, primordial even, like lava. And it is a loaded word if, say, you're Indigenous or descend from a people whose land was taken from them.

A team of geologists has found for the first time evidence that two ancient, continent-sized, ultrahot structures hidden beneath the Earth have shaped the planet's magnetic field for the past 265 million years. These two masses, known as large low-shear-velocity provinces (LLSVPs), are part of the catalog of the planet's most enormous and enigmatic objects. Current estimates calculate that each one is comparable in size to the African continent, although they remain buried at a depth of 2,900 kilometers.

Remembering the life and work of the geologist George Poulett Scrope, and salmon stories in this week's pick from the Nature archive.

The population of super-Earths and sub-Neptunes, and the origin of the radius valley that separates these two classes of planets, is best explained by cores that are made of an Earth-like composition without a substantial amount of accreted ice8,9,10,11. For sub-Neptunes, the hydrogen-rich envelope overlies the rocky core for billions of years, whereas for super-Earths, the envelope may be retained for about 100 Myr (refs. ).