Earth's Early History
Differentiation of the core from the mantle early in the Earth's history was possible because the planet was ___ at the time.
Because the planet was molten at the time.
What is a mineral and how is it different from a rock?
A mineral is a naturally occurring, inorganic solid with a definite chemical composition and an orderly crystalline structure. A rock, on the other hand, is made of one or more minerals.
Geologists use physical properties to identify minerals. (Identify the properties?)
Specific gravity refers to the density of a mineral compared to water. Habit describes the typical crystal shape a mineral forms. Cleavage is the tendency of a mineral to break along flat, smooth planes. Fracture describes how a mineral breaks when it does not have cleavage, often producing irregular or curved surfaces. Luster refers to how light reflects off a mineral’s surface, such as metallic or nonmetallic. Streak is the color of a mineral’s powdered form. Hardness is a mineral’s resistance to scratching.
What are tectonic plates made of?
Tectonic plates are made of the lithosphere, which consists of the crust and the rigid uppermost part of the mantle.
What is the theory of plate tectonics?
The theory of plate tectonics states that the Earth’s lithosphere is divided into large plates that move over the asthenosphere. Their interactions cause earthquakes, volcanoes, and mountain building.
How did the moon form?
The most widely accepted explanation is the Giant Impact Hypothesis. About 4.5 billion years ago, a Mars-sized object collided with the early Earth. Debris from this collision was ejected into orbit and eventually came together to form the moon.
What is a gem?
Liz. :) And the real answer is, A gem is a rare and valuable mineral that is cut and polished for use in jewelry.
What is the Mohs Scale?
The Mohs Scale is a scale of mineral hardness ranging from 1 to 10, where 1 is talc (the softest mineral) and 10 is diamond (the hardest).
What is the difference between the lithosphere and the asthenosphere?
The lithosphere is rigid and brittle and forms the tectonic plates. The asthenosphere lies beneath the lithosphere and is partially molten and plastic, allowing the plates to move over it.
Why are certain scientists important to Earth science?
Alfred Wegener proposed the idea of continental drift, suggesting that continents were once joined together in a supercontinent called Pangaea. Harry Hess proposed seafloor spreading, explaining how new ocean crust forms at mid-ocean ridges. Robert S. Dietz helped develop and refine the concept of seafloor spreading.
How did the earth form?
Earth formed about 4.6 billion years ago from a rotating cloud of gas and dust called solar nebula. Through a process called accretion, dust particles stuck together, forming larger bodies called planetesimals. These collided and grew into protoplanets, eventually forming Earth.
What is a polymorph?
A polymorph refers to minerals that have the same chemical composition but different crystal structures. For example, diamond and graphite are both made of carbon but have different atomic arrangements.
What are the major internal layers of the Earth?
From top to bottom, the main layers are the crust, mantle, outer core, and inner core. The crust is the outermost and thinnest layer. The continental crust is about 35–70 km thick, while the oceanic crust is about 5–10 km thick. The mantle lies beneath the crust and is about 2,900 km thick, making it the largest layer. Below the mantle is the outer core, which is about 2,200 km thick and is liquid. At the very center is the inner core, which has a radius of about 1,220 km and is solid.
How are continental and oceanic crust similar and different?
Both are solid and part of the lithosphere. However, continental crust is thicker, less dense, and mainly granitic in composition. Oceanic crust is thinner, denser, and mainly basaltic.
What is continental drift?
Continental drift is the hypothesis that continents were once connected and later moved apart.
When the Earth formed, what was it like? When did that happen?
When the Earth first formed around 4.6 billion years ago, it was extremely hot, largely molten, heavily bombarded by meteorites, and had intense volcanic activity. There was no oxygen-rich atmosphere at that time.
What are silicates and what is the silica-oxygen tetrahedron?
Silicates are minerals made primarily of silicon and oxygen. The basic building block of silicate minerals is the silica-oxygen tetrahedron, which consists of one silicon atom bonded to four oxygen atoms in a pyramid shape. These tetrahedra link together in different ways by sharing oxygen atoms and other cations to form a wide variety of silicate minerals.
Which layer is on top?
The crust is the top layer. The mantle is the middle layer. The core (outer and inner) makes up the deepest layers.
Earth produces a magnetic field that deflects the solar wind. Are the Magnetic North Pole and Geographic North Pole the same?
No, they are not the same location. The magnetic pole moves over time. The magnetic field is generated by the movement of liquid iron in the outer core, which creates electric currents and produces a geodynamo effect.
What is seafloor spreading?
Seafloor spreading is the process by which new oceanic crust forms at mid-ocean ridges and spreads outward.
Hello :) Free Space!
What percentage of the continental crust is made of silicates?
About 90 percent of the continental crust consists of silicate minerals.
Which layers are solid and which are liquid?
The crust, mantle, and inner core are solid. The outer core is liquid.
What are continental plates?
Continental plates are large pieces of lithosphere that include continental crust and the underlying upper mantle.
What is plate tectonics?
Plate tectonics is the modern theory that combines continental drift and seafloor spreading into one comprehensive explanation of plate movement.