Dec 3, 2020 10:00 PM
Continents ‘prone to destruction’ in infancy
https://cosmosmagazine.com/earth/earth-s...n-infancy/
EXCERPTS: Australian geologists have discovered why no trace remains of the continents formed in the first 500 million years of Earth’s history. Their paper, published in the journal Nature, uses mathematical modelling to simulate the conditions of the early Earth and answer key questions about how the continental plates – in particular, cratons – evolved.
[...] Though the Earth is 4.5 billion years old, geologists only have a very hazy idea of the planet’s first 1.5 billion years of existence – which was a crucial period, according to the study’s lead author, Fabio Capitanio, from Monash University. “This was the time of formation of the first continents, the emergence of land, the development of the early atmosphere, and the appearance of primordial life – all of which are the result of the dynamics of our planet’s interiors,” he explains.
[...] In the Hadean – the first 500 million years of the planet – the crust appears to have been completely recycled so almost no trace remains today, while in the following billion years, the Archean era, we begin to see rigid continental “keels” forming beneath bits of crust, allowing these layered slabs to be preserved as cratons. “The geological record suggests that the very early continents did not survive and were recycled in the planet’s interiors, yet this trend dramatically inverted approximately four billion years ago, when the most enduring piece of continents, cratons, appeared,” Capitanio. says
[...] Their simulations show that the release of internal primordial heat from the planet’s formation – which would have been three or four times greater than the amount released now – caused the upper part of the Earth’s mantle to melt. This oozed up to the surface as magma, or molten rock, to form new crust. The parts of the mantle left below were depleted and went on to form rigid “rafts” or “keels” that shielded the crust above – thus creating the cratons we see today.
“Our results explain that continents remained weak and prone to destruction in their infancy, about 4.5 to 4 billion years ago, then progressively differentiated and became rigid over the next billion years to form the core of our modern continents,” Capitanio says... (MORE - details)
Electronic waste is on the decline in the US, but it's only because TVs are getting smaller
https://www.zmescience.com/science/elect...t-smaller/
EXCERPTS: Electronic waste is already well-established a global environmental problem, with millions of TVs and cellphones ending up in landfills or incinerated every year instead of being recycled. [...] There is no federal-level e‐waste policy in the US — instead, e‐waste management is handled through a patchwork of state regulations. This has limited the number of studies on the issue, with most focused on other parts of the world. In the European Union, for example, legislations are uniform for all nations.
In a novel study, researchers from Yale University found that residential e-waste in the US is declining, with a net mass reduction of almost 10% since its peak in 2015 — but this isn’t really as good a sign as it seems. Instead, it’s mainly due to the disappearance of bulky cathode-ray tube (CRT) televisions and computer monitors and their replacement with thinner electronics.
CRT displays in the waste stream peaked in 2011, just a few years after the digital transition in television broadcast signals and the rapid switch to digitally-enabled flat-panel TVs. While CRT displays have declined in the waste stream since their peak, these devices still make up about one-third of the total mass of e‐waste.
[...] Now, the contribution of flat panel display devices to total e‐waste is also becoming increasingly significant and will soon surpass CRTs with about 34% contribution to the total waste stream mass. Flat panels often have higher failure rates and shorter lifespans, leading to more frequent replacement cycles. Callie Babbitt, one of the study’s authors, said that the decline in bulkier displays means that e-waste regulations will have to be rethought.... (MORE -details)
https://cosmosmagazine.com/earth/earth-s...n-infancy/
EXCERPTS: Australian geologists have discovered why no trace remains of the continents formed in the first 500 million years of Earth’s history. Their paper, published in the journal Nature, uses mathematical modelling to simulate the conditions of the early Earth and answer key questions about how the continental plates – in particular, cratons – evolved.
[...] Though the Earth is 4.5 billion years old, geologists only have a very hazy idea of the planet’s first 1.5 billion years of existence – which was a crucial period, according to the study’s lead author, Fabio Capitanio, from Monash University. “This was the time of formation of the first continents, the emergence of land, the development of the early atmosphere, and the appearance of primordial life – all of which are the result of the dynamics of our planet’s interiors,” he explains.
[...] In the Hadean – the first 500 million years of the planet – the crust appears to have been completely recycled so almost no trace remains today, while in the following billion years, the Archean era, we begin to see rigid continental “keels” forming beneath bits of crust, allowing these layered slabs to be preserved as cratons. “The geological record suggests that the very early continents did not survive and were recycled in the planet’s interiors, yet this trend dramatically inverted approximately four billion years ago, when the most enduring piece of continents, cratons, appeared,” Capitanio. says
[...] Their simulations show that the release of internal primordial heat from the planet’s formation – which would have been three or four times greater than the amount released now – caused the upper part of the Earth’s mantle to melt. This oozed up to the surface as magma, or molten rock, to form new crust. The parts of the mantle left below were depleted and went on to form rigid “rafts” or “keels” that shielded the crust above – thus creating the cratons we see today.
“Our results explain that continents remained weak and prone to destruction in their infancy, about 4.5 to 4 billion years ago, then progressively differentiated and became rigid over the next billion years to form the core of our modern continents,” Capitanio says... (MORE - details)
Electronic waste is on the decline in the US, but it's only because TVs are getting smaller
https://www.zmescience.com/science/elect...t-smaller/
EXCERPTS: Electronic waste is already well-established a global environmental problem, with millions of TVs and cellphones ending up in landfills or incinerated every year instead of being recycled. [...] There is no federal-level e‐waste policy in the US — instead, e‐waste management is handled through a patchwork of state regulations. This has limited the number of studies on the issue, with most focused on other parts of the world. In the European Union, for example, legislations are uniform for all nations.
In a novel study, researchers from Yale University found that residential e-waste in the US is declining, with a net mass reduction of almost 10% since its peak in 2015 — but this isn’t really as good a sign as it seems. Instead, it’s mainly due to the disappearance of bulky cathode-ray tube (CRT) televisions and computer monitors and their replacement with thinner electronics.
CRT displays in the waste stream peaked in 2011, just a few years after the digital transition in television broadcast signals and the rapid switch to digitally-enabled flat-panel TVs. While CRT displays have declined in the waste stream since their peak, these devices still make up about one-third of the total mass of e‐waste.
[...] Now, the contribution of flat panel display devices to total e‐waste is also becoming increasingly significant and will soon surpass CRTs with about 34% contribution to the total waste stream mass. Flat panels often have higher failure rates and shorter lifespans, leading to more frequent replacement cycles. Callie Babbitt, one of the study’s authors, said that the decline in bulkier displays means that e-waste regulations will have to be rethought.... (MORE -details)