Geology notes

Geology notes

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18/04/2022

How are Iceland's volcanoes related to plate tectonics?
Iceland seems to be what geologists refer to as a large igneous province, built up by mafic magmas from the earth’s upper mantle. These magmas are coming up from the mantle apparently at a hotspot that happens to coincide with the mid Atlantic Ocean spreading ridge, where the North American and Eurasian Plates are being pulled apart.

12/04/2022

What would happen if the Earth’s core was split in half?

The earth’s core is viscous, molten metal. If it were split, it would just flow back together. However, that might result in calamitous harmonics due to the waves splashing back and forth. The probability is that the surface or mantle of the earth could be affected by terrible earthquakes.

09/04/2022

What is the grading of sand?

Grading is basically a range of particle size. if any sand consists of all size variations such that coarser(>5mm), medium(1–5mm), and finer(

03/04/2022

everyone knows about

02/04/2022

Primarily “Soil Erosion” occurs when soil structure becomes loose. Had it been a natural process? We would be left with no soul after thousands of years of land use. But it has happened vigorously as human being considered itself as MASTER of the Food Chain. Further, it aggravated when mankind started using first forest wealth unabatedly and subsequently land cover for urbanisation and industrialisation. These processes in turn depleted vegetation cover from soil, reduced water table and exposed it to the extent of soil degradation.

29/03/2022

Who know about Geological Process?
(Do answer in comment box)

25/03/2022

What type of rock is Everest?

Everest is composed of multiple layers of rock folded back on themselves (nappes). Rock on the lower elevations of the mountain consists of metamorphic schists and gneisses, topped by igneous granites.

The sedimentary rock layers found on Mount Everest include limestone, marble, shale, and pelite; below them are older rocks including granite, pegmatite intrusions, and gneiss, a metamorphic rock. The upper formations on Mount Everest and neighboring Lhotse are filled with marine fossils.

24/03/2022

What is the difference between magma and lava in volcanology?

Magma is the lava which is still trapped inside and Lava is the magma that has escaped the Magma chamber and is now flowing on the earth's surface. Both of them are just molten rock. Magma becomes lava when it gets an 'upgrade’ by escaping out of the volcano.

24/03/2022

How do you think the location of a volcano affects the magma composition?

21/03/2022

What is the process by which rocks are slowly broken into smaller pieces?

Hot springs reveal where continental plates collide beneath Tibet 20/03/2022

Hot springs reveal where continental plates collide beneath Tibet.

By analyzing the chemistry of over 200 geothermal springs, researchers have identified where the Indian Plate ends beneath Tibet, debunking some long-debated theories about the process of continental collision.

In the classic example of mountain-building, the Indian and Asian continental plates crashed -- and continue colliding today -- to form the world's largest and highest geologic structures: the Himalayan Mountains and the Tibetan Plateau.

Despite the importance of these formations, which influence the global climate through atmospheric circulation and seasonal monsoons, experts have proposed contradicting theories about how tectonic plates below the surface created the iconic behemoths. Now, using geochemical data from 225 hot springs, scientists have mapped the boundary between the Indian and Asian continental plates, shedding light on processes occurring deep below the surface. The findings, which have implications for mineral formation, appear in the current issue of Proceedings of the National Academy of Sciences.

"A principal debate amongst geologists is whether or not continental collision looks like oceanic collision," said senior study author Simon Klemperer, a geophysics professor at Stanford's School of Earth, Energy & Environmental Sciences (Stanford Earth). "Because there are too few measurements, seismology wasn't giving us the answer -- that's why I took up geochemistry as a totally different way to measure things."

Klemperer has spent the better part of a decade traveling to Tibet and India to collect samples to support his theory that chemicals bubbling to the surface could be used to understand what's happening 50 miles below. He and his colleagues tracked down remote geothermal springs for hundreds of miles across the mountains and plateau -- about the distance from Canada to Mexico in the western U.S.

Using the noble gas helium, which doesn't react with other chemicals, the study authors determined which springs originated from each continental plate. One helium isotope signature revealed when the gas came from the hot mantle -- the Asian plate -- while a different signature indicated the much colder Indian plate. The research shows that the colder plate is only detected in the south, beneath the Himalayas, while further north, India is no longer touching Tibet above it -- it's separated from Tibet by a wedge of hot mantle. The results indicate that an old theory that the Indian plate lies flat beneath Tibet is no longer tenable.

"It's amazing that we now have this remarkably well-defined boundary just a few kilometers wide at the surface above a plate boundary that is 100 kilometers deep," Klemperer said.

Subduction vs. collision

In oceanic subduction, material in the subsurface is recycled into the Earth's mantle when the cooler, heavier plate dives under a continental plate and sinks. The process occurs in zones like the Ring of Fire, which is known for frequent earthquakes and active volcanoes.

In continental collision, researchers have hypothesized that subduction of ocean crust dragged the two continents closer together until they collided, closing up the subduction zone for mountain building to occur. This evidence of the continental boundary below Tibet introduces the possibility that the continental crust is releasing fluids and melting -- just as it would happen in oceanic subduction.

"This says that we shouldn't be looking at continental collision and oceanic subduction as two different things -- we should be looking at them as the same thing with somewhat different flavors because geometrically, they look the same," Klemperer said.

Tectonic sea change

In the 1960s, the theory of plate tectonics revolutionized the Earth sciences by explaining how geologic plates drift apart and into each other, causing mountain building, volcanic eruptions and earthquakes. But researchers understand little about why plates move the way they do.

Klemperer said the new findings add an important element of understanding, with potential ramifications about what controls the convection that drives plate tectonics. Even though it's a continental collision, the Indian plate diving into the mantle helps control the pattern of convection -- it changes the way we understand how elements and rock types are distributed and re-distributed on the Earth, he said.

The study builds on previous research in which Klemperer and his colleagues imaged the Himalaya collision zone using seismic data and found that as the Indian tectonic plate moves from the south, the thickest and strongest part of the plate dips beneath the Tibetan plateau and causes tears in the Indian plate. Those tears were in the same location as helium fluxes in the hot springs.

"We're seeing the same processes through these different lenses, and we have to figure out how to put them together," Klemperer added.

Mineral implications

Ever since the Spaniards conquered South America in search of gold, civilizations have known about rich mineral deposits in places like the Andes Mountains, which are part of the Ring of Fire. Southern Tibet has more recently also been recognized as a rich mineral province, with gold, copper, lead, zinc and other deposits, which are difficult to explain using only the old models of continental collision.

"The largest copper deposits occur in granites that are produced by melting of the hot mantle wedge -- that shouldn't happen in continental collision if it looks like the old model, but we know it did happen because we have all these minerals in Tibet," Klemperer said. "Our work tells us about the large-scale tectonics of continental collision and suggests that we might expect to see the same sort of mineral deposits in continental-collision environments as oceanic-subduction environments."

As the only active continental collision on our planet, the Himalayas and Tibet also offer a glimpse into how other mountain ranges have formed in the past and may form in the future.

"Australia is just beginning to collide with the Indonesian block -- that's continental collision beginning to happen," Klemperer said. "Tibet is the type-example to be solved and we hope it's an analog for everywhere else about how this happens on Earth."

Klemperer is also a professor, by courtesy, of geological sciences. Tianze Liu, who worked on the project as a Stanford PhD student, is a co-author on the study. Additional co-authors are from the Chinese Academy of Sciences, The Ohio State University, the University of New Mexico and the Scripps Institution of Oceanography.

This research was supported by grants from the National Science Foundation, the Second Tibetan Plateau Scientific Exploration and Research Program, the Strategic Priority Research Program of the Chinese Academy of Sciences, National Geographic and the Stanford International Office.

Source :https://www.sciencedaily.com/releases/2022/03/220314154424.htm

Hot springs reveal where continental plates collide beneath Tibet By analyzing the chemistry of over 200 geothermal springs, researchers have identified where the Indian Plate ends beneath Tibet, debunking some long-debated theories about the process of continental collision.

20/03/2022

What is the layer of earth that is liquid?

The earth has 4 layers, from the shallowest to the deepest - the crust, the mantle, the outer core and the inner core. The outer core and some parts of the deep mantle are made from liquid molten matels

17/03/2022

Why are there tiny black dots in Rose Quartz Stone?

Pure rose quartz has no “black dots”. The black dots in the specimen you refer to must be what geologists call “inclusions”. These are tiny crystals of other minerals which were captured inside the rose quartz at the time it was forming from silica v***r or silica liquid. they must have crystallized at approximately the same time. A common inclusion found in quartz crystals is the mineral rutile. Rutile is Titanium oxide and often occurs as needle-shaped crystals within the quartz. Another common inclusion in the mineral tourmaline. Those are often black crystals.

22/01/2022

What Is An Unconformity In Geology?

An unconformity occurs when there is an erosion of a layer or layers of deposited rock followed by the deposition of new sedimentary rock on top. It is called an unconformity because the ages of the layers of rock that are abutting each other are discontinuous at the unconformity. The expected age of layer or layers of rock is/are missing due to the erosion; and, some period in geologic time is not represented.

There are three types of unconformities:

Disconformity: Sedimentary layer deposited over eroded horizontal sedimentary layer

Angular unconformity: Sedimentary layer deposited over eroded angular (tilted or folded) rock

Nonconformity: Sedimentary layer deposited over eroded igneous or metamorphic rock

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