However, it was not until the 16th and 17th centuries that a scientific understanding of planet Earth and its structure truly began to advance. Between this and an inner sphere, he reasoned there was an air gap of the same distance. To avoid collision, he claimed that the inner sphere was held in place by the force of gravity. The model included two inner concentric shells around an innermost core, corresponding to the diameters of the planets Mercury, Venus, and Mars respectively.
However, his work was instrumental to the development of geography and theories about the interior of the Earth during the 17th and 18th centuries. Another important factor was the debate during the 17th and 18th centuries about the authenticity of the Bible and the Deluge myth. This propelled scientists and theologians to debate the true age of the Earth, and compelled the search for evidence that the Great Flood had in fact happened.
Combined with fossil evidence, which was found within the layers of the Earth, a systematic basis for identifying and dating the Earth's strata began to emerge. The development of modern mining techniques and growing attention to the importance of minerals and their natural distribution also helped to spur the development of modern geology.
In , the National Museum of Natural History in France created the first teaching position designated specifically for geology. This was an important step in further promoting knowledge of geology as a science and in recognizing the value of widely disseminating such knowledge.
By the s, chemistry was starting to play a pivotal role in the theoretical foundation of geology, and theories began to emerge about how the Earth's layers were formed. One popular idea had it that liquid inundation, like the Biblical Deluge, was responsible for creating all the geological strata.
Those who accepted this theory became known popularly as the Diluvianists or Neptunists. Another thesis slowly gained currency from the s forward, which stated that instead of water, strata had been formed through heat or fire.
Those who followed this theory during the early 19th century referred to this view as Plutonism, which held that the Earth formed gradually through the solidification of molten masses at a slow rate. These theories together led to the conclusion that the Earth was immeasurably older than suggested by the Bible. In the early 19th century, the mining industry and Industrial Revolution stimulated the rapid development of the concept of the stratigraphic column — that rock formations were arranged according to their order of formation in time.
Concurrently, geologists and natural scientists began to understand that the age of fossils could be determined geologically i. During the imperial period of the 19th century, European scientists also had the opportunity to conduct research in distant lands. Darwin's discovery of giant fossils during the voyage helped to establish his reputation as a geologist, and his theorizing about the causes of their extinction led to his theory of evolution by natural selection, published in On the Origin of Species in During the 19th century, the governments of several countries including Canada, Australia, Great Britain and the United States funded geological surveying that would produce geological maps of vast areas of the countries.
By this time, the scientific consensus established the age of the Earth in terms of millions of years, and the increase in funding and the development of improved methods and technology helped geology to move farther away from dogmatic notions of the Earth's age and structure. By the early 20th century, the development of radiometric dating which is used to determine the age of minerals and rocks , provided the necessary the data to begin getting a sense of the Earth's true age.
By the turn of the century, geologists now believed the Earth to be 2 billion years old, which opened doors for theories of continental movement during this vast amount of time. In , Alfred Wegener proposed the theory of Continental Drift, which suggested that the continents were joined together at a certain time in the past and formed a single landmass known as Pangaea.
In accordance with this theory, the shapes of continents and matching coastline geology between some continents indicated they were once attached together.
Research into the ocean floor also led directly to the theory of Plate Tectonics, which provided the mechanism for Continental Drift. Geophysical evidence suggested lateral motion of continents and that oceanic crust is younger than continental crust. This geophysical evidence also spurred the hypothesis of paleomagnetism, the record of the orientation of the Earth's magnetic field recorded in magnetic minerals. Then there was the development of seismology, the study of earthquakes and the propagation of elastic waves through the Earth or through other planet-like bodies, in the early 20th century.
By measuring the time of travel of refracted and reflected seismic waves, scientists were able to gradually infer how the Earth was layered and what lay deeper at its core. For example, in , Harry Fielding Ried put forward the "elastic rebound theory", based on his studies of the San Fransisco earthquake.
This theory, which stated that earthquakes occur when accumulated energy is released along a fault line, was the first scientific explanation for why earthquakes happen, and remains the foundation for modern tectonic studies.
Then in , English scientist Harold Jeffreys claimed that below the crust, the core of the Earth is liquid, based on his study of earthquake waves. And then in , Danish seismologist Inge Lehmann went a step further and determined that within the earth 's liquid outer core, there is a solid inner core. By the latter half of the 20th century, scientists developed a comprehensive theory of the Earth's structure and dynamics had formed. As the century played out, perspectives shifted to a more integrative approach, where geology and Earth sciences began to include the study of the Earth's internal structure, atmosphere, biosphere and hydrosphere into one.
This was assisted by the development of space flight, which allowed for Earth's atmosphere to be studied in detail, as well as photographs taken of Earth from space. Geological Survey, began supplying satellite images that provided geologically detailed maps, and have been used to predict natural disasters and plate shifts.
The Earth can be divided into one of two ways — mechanically or chemically. Mechanically — or rheologically, meaning the study of liquid states — it can be divided into the lithosphere, asthenosphere, mesospheric mantle, outer core, and the inner core.
But chemically, which is the more popular of the two, it can be divided into the crust, the mantle which can be subdivided into the upper and lower mantle , and the core — which can also be subdivided into the outer core, and inner core.
This is due to the relative melting points of the different layers nickel—iron core, silicate crust and mantle and the increase in temperature and pressure as depth increases. At the surface, the nickel-iron alloys and silicates are cool enough to be solid. The InSight mission is expected to launch in to do a deep drill into the surface of Mars and yield more information about the interior. Some planned rovers also carry lengthy drills, such as the ExoMars rover that launches in Venus has an extremely thick atmosphere that blocks visible light from reaching the surface, which means it requires radar to look at the surface.
The surface appears fresh and young — no more than million years old — due to the amount of volcanic activity on Venus' hellishly hot surface. While Venus likely has a crust, mantle and core similar to Earth, its magnetic field is very weak compared to Earth's. That may be because the core spins sluggishly to generate the magnetic field, or because there is no core at all. Mars is a cold planet whose atmosphere is not thick enough to let liquid water flow at the surface although briny water is a possibility.
It has a crust covered by dust; it's believed the crust is solid, with no plate tectonics. This allowed Mars to build up huge volcanoes on its surface, such as Olympus Mons. However, the Martian volcanoes appear dormant — why is still poorly understood. Underneath the surface, Mars likely has a mantle and a core ; since Mars has no global magnetic field, the core probably does not spin. The Mantle.
The mantle is the layer located directly under the sima. It is the largest layer of the Earth, miles thick. The mantle is composed of very hot, dense rock. This layer of rock even flows like asphalt under a heavy weight. This flow is due to great temperature differences from the bottom to the top of the mantle.
The movement of the mantle is the reason that the plates of the Earth move! The temperature of the mantle varies from degrees Fahrenheit at the top to about degrees Fahrenheit near the bottom! Convection Currents. The mantle is made of much denser, thicker material, because of this the plates "float" on it like oil floats on water. Many geologists believe that the mantle "flows" because of convection currents. Convection currents are caused by the very hot material at the deepest part of the mantle rising, then cooling, sinking again and then heating, rising and repeating the cycle over and over.
The next time you heat anything like soup or pudding in a pan you can watch the convection currents move in the liquid. When the convection currents flow in the mantle they also move the crust.
The crust gets a free ride with these currents. A conveyor belt in a factory moves boxes like the convection currents in the mantle moves the plates of the Earth. Outer Core. The core of the Earth is like a ball of very hot metals. Fun Fact: Without the outer core's magnetic field our planet would resemble the barren planet of Mars.
The inner core is the deepest layer on Earth. It is also made up of iron and nickel but the pressure is so high that it is no longer liquid. Earth's inner core is 1, to 1, km thick. Fun Fact : Earth's inner core is growing in size by 1mm per year. Eventually, the entire outer core will solidify as part of the inner core. But don't worry, that won't happen for many billions of years.
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