Science

• Earth belongs to a group of planets that revolve around the sun.
• The Earth consists of three major layers: The crust, the mantle, and the core.
• The crust is made of solid rocks rich in silicon, aluminum, magnesium and other elements.
• The crust is the thinnest layer of the Earth.
• The crust found under the ocean is called oceanic crust.
• The oceanic crust is 8-10 km thick.
• The crust carrying a mass of land is called continental crust.
• The continental crust is about 32-35 km thick.
• The oceanic crust is denser than the continental crust. This difference in density is primarily to their composition.
• The continental crust is made of a higher percentage of silicon, oxygen amd aluminum
• The rocks that make up the continental crust are mostly granite and ryolite.
• The oceanic crust is made of denser rocks called basalt and gabbro.
• The second and the middle layer of the Earth is called the mantle.
• Between the crust and the mantle, is a thin boundary called Mohorovicic discontinuity.
• The Mohorovicic discontinuity was named after the Croatian scientist named Andrija Mohorovicic who discovered it in 1909.
• The Mantle is the thickest layer of the Earth.
• The Mantle is 2,900 km thick
• The Mantle is divided in 2 parts, the upper mantle and the lower mantle.
• Unlike the crust, the mantle is not pure solid. A portion of this layer is made of molten rocks called magma. This part is called the asthenosphere.
• The asthenosphere is a portion of the mantle found above the Mohorovicic discontinuity and beneath the crust.
• Between the mantle and the innermost layer is a region called Gutenberg discontinuity. This region was named after a German scientist, Beno Gutenberg.
• The core is the innermost layer of the earth.
• The core is divided into 2 parts, the inner core and the outer core.
• The inner core is made up of solid iron and nickel. It is 1216 km thick. The high pressure in the inner core makes it solid.
• The outer core is composed of liquid iron and nickel, it is 2,270 km thick. The presence of a large amount of iron in the outer and inner core explains why there is a magnetic field on earth.
• Alfred wegener believed that the Earth was once made up of a supercontinent called Pangea. Pangea in greek means "all of the lands".
• According to Wegener, Pangea broke into several masses of land. Which leads to him proposing the continental drift theory in 1912.
• Evidences that support the Continental drift theory is Rock evidence, Glacial evidence, and the Fossil evidence.
• The Continental drift theory did not provide sufficient explanation as to how & why the continents moved & formed.
• A sonar device is a device the bounces off sound waves from the ocean floor.
• Trenches are long, narrow, and deep regions on the ocean floor. They are formed when an oceanic crust collides with a continental crust.
• A mid-ocean ridga is a chain of underwater mountains.
• A mid-ocean ridge is a chain of underwater mountains.
• A rift is a valley between 2 ridges. The rift serves as an opening in the formation of a new crust.
• The Evidences supporting the Seafloor Spreading Theory is the age of rocks and the pattern of parallel in magnetic stripes on rocks.
• Plate tectonics theory refer to the drifting of continents.
• According the the plate tectonics theory the earths lithosphere is divided into large pieces called plates. The six major lithospheric plates, the American, African, Eurasian, Antartic, Indian, and the Pacific.
• These plates vary in size and shape. They are less dense than the asthenosphere.
• The movement of these plates is called tectonics.
• A divergent boundary is found where plates

  move away from each other.