BRITISH & EXOTIC MINERALOGY
All 2,242 illustrations from James Sowerby’s compendium of knowledge about mineralogy in Great Britain and beyond, drawn 1802–1817 and arranged by color.

Plate tectonics may have its origins in impacts, based on new data from Australia.

NASA researchers have an estimate of the power of a massive volcanic eruption that took place on Saturday near the island nation of Tonga.

"We come up with a number that's around 10 megatons of TNT equivalent," James Garvin, the chief scientist at NASA's Goddard Space Flight Center, told NPR. //

Hunga Tonga-Hunga Ha'apai was completely destroyed by Saturday's explosion, says Dan Slayback, a research scientist for NASA's Goddard, as well as Science Systems and Applications Inc. Slayback says the blast was so massive it even appears to have taken chunks out of the older islands nearby.

"They weren't ash — they were solid rock, blown to bits," he says. "It was quite amazing to see that happen." //

He suspects the explosion was triggered by a sudden change in the subterranean plumbing, which caused seawater to flood in.

"When you put a ton of seawater into a cubic kilometer of liquid rock, things are going to get bad fast," he says.

If you saw a rock on Earth like this, and you picked it up, it shouldn't be that heavy," another Melbourne Museum geologist, Bill Birch, told The Sydney Morning Herald in 2019.

The ancient supercontinent Rodinia may be responsible.

Visitors to the Crater of Diamonds can find much more than diamonds here. One of the most common rocks found at the park is also one of the rarest to find beyond the borders of the crater. Lamproite is the volcanic material that erupted from the park’s diamond-bearing pipe around 100 million years ago. Four types of lamproite can be found at the park today, but not all are diamond-bearing. Knowing where each type of lamproite is found can provide insight into the park’s fascinating geological history.

Earth generates heat. The deeper you go, the higher the temperature. At 25km down, temperatures rise as high as 750°C; at the core, it is said to be 4,000°C. Humans have been making use of hot springs as far back as antiquity, and today we use geothermal technology to heat our apartments. Volcanic eruptions, geysers and earthquakes are all signs of the Earth's internal powerhouse. //

The average heat flow from the earth's surface is 87mW/m2 – that is, 1/10,000th of the energy received from the sun, meaning the earth emits a total of 47 terawatts, the equivalent of several thousand nuclear power plants. The source of the earth's heat has long remained a mystery, but we now know that most of it is the result of radioactivity. //

The decay of one uranium-238 nucleus, for example, releases an average of 6 neutrinos, and 52 megaelectronvolts of energy carried by the released particles that then lodge in matter and deposit heat. Each neutrino carries around two megaelectronvolts of energy. According to standardized measures, one megaelectronvolt is equivalent to 1.6 10-13 joules, so it would take around 1025 decays per second to reach the earth's total heat. The question is, can these neutrinos be detected? //

Two recent experiments have added to the research: KamLAND, a detector weighing 1,000 metric tons underneath a Japanese mountain, and Borexino, which is located in a tunnel under the Gran Sasso mountain in Italy and weighs 280 metric tons. Both use "liquid scintillators." To detect neutrinos from the earth or the cosmos, you need a detection method that is effective at low energies; this means exciting atoms in a scintillating liquid. Neutrinos interact with protons, and the resulting particles emitted produce observable light.

KamLAND has announced more than 100 events and Borexino around 20 that could be attributed to geoneutrinos, with an uncertainty factor of 20-30%. We cannot pinpoint their source, but this overall measurement—while fairly rough—is in line with the predictions of the simulations, within the limits of the low statistics obtained.

Therefore, the traditional hypothesis of a kind of nuclear reactor at the center of the earth, consisting of a ball of fissioning uranium like those in nuclear power plants, has now been excluded. Fission is not a spontaneous radioactivity but is stimulated by slow neutrons in a chain reaction.

Past and future trends in global mean temperature spanning the last 67 million years. Oxygen isotope values in deep-sea benthic foraminifera from sediment cores are a measure of global temperature and ice volume. Temperature is relative to the 1961-1990 global mean. Data from ice core records of the last 25,000 years illustrate the transition from the last glacial to the current warmer period, the Holocene. Historic data from 1850 to today show the distinct increase after 1950 marking the onset of the Anthropocene. Future projections for global temperature for three Representative Concentration Pathways (RCP) scenarios in relation to the benthic deep-sea record suggest that by 2100 the climate state will be comparable to the Miocene Climate Optimum (~16 million years ago), well beyond the threshold for nucleating continental ice sheets. If emissions are constant after 2100 and are not stabilized before 2250, global climate by 2300 might enter the hothouse world of the early Eocene (~50 million years ago) with its multiple global warming events and no large ice sheets at the poles. Credit: Westerhold et al., CENOGRID

Originally named by John Wesley Powell, the Colorado Plateau comprises a series of tablelands (plateaus or mesas) located within an immense basin surrounded by highlands. Stream valleys that are typically narrow and widely spaced dissect the region, as do larger valleys, including the most spectacular – the Grand Canyon.

The Grand Canyon is the largest stream valley dissecting the tablelands of the Colorado Plateau The Grand Canyon is the largest stream valley dissecting the tablelands of the Colorado Plateau

NPS / Kristen M. Caldon

23 September 2019|Nature

The Veryovkina Cave is the deepest known cave on Earth. It took half a century and about 30 expeditions for Russian cave explorers to reach its record depth of 2,212 meters. Speleologists still think there is more to be discovered.