- 2947 - CALIFORNIA - how the land was made? Before California was formed, the continent was called “Laurentia” on its journey back and forth across the equator, as it joined and was separated from the supercontinents. Over billions of years, Laurentia or North America, the continent took its form through many spectacular collisions and massive rifts.
--------------------------------- Is Your Donkey In The Well?
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- One day a farmer's donkey fell down into a well.
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- The animal cried piteously for hours as the farmer tried to figure out what to do.
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- Finally he decided the animal was old and the well needed to be covered up anyway,
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- It just wasn't worth it to retrieve the donkey. He invited all his neighbors to come over and help him.
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- They each grabbed a shovel and began to shovel dirt into the well.
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- At first, the donkey realized what was happening and cried horribly.
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- Then, to everyone's surprise, he quieted down. A few shovel loads later,
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- The farmer looked down the well, and was astonished at what he saw.
As every shovel of dirt hit his back, the donkey did something amazing.
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- He would shake it off and take a step up. As the farmer's neighbors continued
to shovel dirt on top of the animal, he would shake it off and take a step up.
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- Pretty soon, everyone was amazed, as the donkey stepped up over the edge of the well and trotted off.
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-------------------------------------- The Moral:
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- Life is going to shovel dirt on you, all kinds of dirt.
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- The trick to getting out of the well is to shake it off and take a step up.
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- Each of our troubles is a stepping stone. We can get out of the deepest wells just by not stopping, never giving up! Shake it off and take a step up.
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------------------ 2947 - CALIFORNIA - how the land was made.
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- We live just 20 miles from the fault line in California, United States, North America. Been here 50 years but the landmass called North America was here before me. It is actually pretty young geologically speaking becoming something close to its current birthday less than 200 million years ago.
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- The continent “Laurentia” was moving back and forth across the equator, as it joined and was separated from the supercontinents. Over billions of years, Laurentia or North America took its form through many spectacular collisions and massive rifts.
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- North American prehistory involves plate tectonics, tectonic plates, continental collisions, and continental breakups. This all happened way before I got here.
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- The central core of present-day North America is its “craton“, that is the oldest, thickest part of the continent. While parts of the craton peek out in Greenland and Canada, in the U.S., thick layers of sedimentary rocks keep most of these ancient assemblages under wraps in the center of the continent.
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- The rocks there are more than two billion years old in places, and were assembled through time as smaller microcontinents and “terranes“, or fragments of crustal material, crashed together.
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- 750 million years ago, the craton, then named Laurentia, was part of a supercontinent called “Rodinia“. Later the Rodinia fragment, Laurentia drifted almost to the South Pole!
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- 542 million years ago, when complex life forms suddenly appear in the fossil record all across the planet, Laurentia was surrounded by ocean and passive margins on all sides. Like today's East Coast, a passive margin has no active collision or boundary between two of Earth's tectonic plates.
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- The continent's brief Cambrian respite ended in the “Ordovician“, when an island chain slammed into the East Coast, raising mountains from Greenland to Mississippi. At that time, the Appalachians were as tall and stunning as the Himalayas are today.
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- A similar collision in the Southwest 370 million years ago twisted rocks throughout what is now Utah and Nevada.
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- The super continent “Pangaea” included almost every giant landmass on Earth. As these pieces of continent crashed together 300 million years ago, mountains continued to rise along what is now the East Coast.
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- The Atlantic Ocean opened 200 million years ago, pushing North America westward. As the continent rifted away from the supercontinent Pangaea, it finally earned the name North America.
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- As the East Coast settled down into a passive margin, with no active tectonics, things were heating up in the West. The widening Atlantic Ocean pushed the continent over the “Panthalassa Ocean“, precursor to today's Pacific.
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- Geoscientists debate the timing and position of subduction zones along western North America. Did it look like today's Andes or like Southeast Asia? Either way, oceanic crust started to disappear as the continent shifted around. Exotic island chains slammed into the western edge, adding to North America's breadth.
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- When North America gobbled up the boundary between the Farallon and Pacific oceanic plates, its western margin shifted from a subduction zone to a transform boundary.
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- This marks the beginning of the San Andreas Fault, which moves side-by-side. With the sudden shutdown of the giant conveyor belt grinding against its margin, the continent relaxed, and the Basin and Range province opened in the Southwest.
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- The last little bits of the “Farallon” plate remain off the Washington and Oregon coast, and further south, near Central America. My house is just half way down this fault line 20 miles inland. Sure hope it stops moving.
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- When Earth was younger, it birthed many new continents then it swallowed them all up, leaving just a few traces behind.
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- These first continents had a knack for living fast and dying young, but in doing so, they paved the way for solid continents that eventually led to the emergence of plate tectonics.
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- The continents remained weak and prone to destruction in their infancy, 4,000,000,000 years ago, and then progressively differentiated and became rigid over the next billion years to form the core of our modern continents.
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- For hundreds of millions of years, the current continents have been more or less stable. They've moved due to plate tectonics, a theory governing the motion of Earth's crust, forming different shapes, such as the ancient super continent “Pangea“.
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- The puzzle pieces of the crust that existed hundreds of millions of years ago mostly still exist today. But very little is known about the continents that existed early on in Earth's history.
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- To learn more about that early history, the researchers used computers to model the interactions of rock and magma in the Earth's crust and below. The modeling showed that the earliest continents formed from parts of the upper mantle, the part of the planet just below the crust, which melted as it reached the surface and then spewed across the landscape in enormous volcanic eruptions. At that time, the planet held a vast reservoir of heat in its interior.
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- The release of internal primordial heat, three to four times that of the present day, caused large melting in the shallow mantle, which was then extruded as magma (molten rock) onto the Earth's surface.
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- But the continents of this period, known as the “Hadean” (4.6 to 4.0 billion years ago), were weak and prone to destruction.
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- Modern continents have a comparatively high tensile strength, meaning it's hard to rip them apart by stretching. But the crust of the Hadean was hotter and thinner, and sat on a squishier upper mantle.
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- Vast rifts would form between these new continents, magma would leak through, and that magma would cover the infant continents, causing the baby continents to sink into the mantle. Meanwhile, new continents were forming from the magma on top of the ones being buried.
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- By the time the “Archean” (4.0 billion to 2.5 billion years ago) began, ending the “Hadean“, the crust that had first formed was almost entirely replaced by the seeds of the modern continents.
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- Those lost Hadean continents made the later, more stable continents possible. The early continents' reabsorption into the shallowest parts of the mantle made that region of the mantle dryer and firmer, forming a foundation on which later continents could safely grow.
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- This scenario could explain how modern plate tectonics, which relies on a firmer foundation and more structurally sound continents, emerged. The model also shows that some pieces of those early continents would remain exposed on the surface, forming stable, thick "roots" in the crust.
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- Those pieces still exist today, and are known as cratons. One of these, Laurentia, forms the core of North America and includes a region covering the Midwest and Great Plains, as well as much of central Canada and Greenland.
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- The emergence of continents at the close of the Hadean also contributed fertilizer that would later help seed life on Earth. Bits of them broke off and entered the atmosphere and oceans, providing necessary nutrients for the life forms that soon emerged.
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December 21, 2020 CALIFORNIA - how the land was made? 2947 ---------------------------------------------------------------------------------------
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