Science Exam Part 1

Earth's Structure

• Earth's structure is divided into four main subsystems: lithosphere, hydrosphere, atmosphere, and biosphere.
• The lithosphere is the solid part of the Earth composed of the crust and the upper mantle.
• The crust is the outermost layer of the Earth, with a thickness of less than 1% of Earth's volume.
• The crust is primarily composed of basalt and granite and has two types: oceanic and continental.
• The mantle lies beneath the crust and extends up to 2,900 km in thickness.
• The mantle is a semi-solid magma layer where the asthenosphere is found, a viscous and slowly flowing layer composed of peridotite.
• The core is the center of the Earth, made up of the liquid outer core and the solid inner core.
• The outer core is composed of molten rock, nickel, and iron.
• The inner core is extremely hot and dense, with temperatures reaching 5,000 degrees Celsius. It plays a crucial role in regulating Earth's temperature.

Plate Tectonics

• Plate tectonics is the theory explaining the movement of Earth's lithospheric plates.
• The theory supports that the lithosphere is broken into several plates that move and interact with each other.
• Several theories explain the movement of lithospheric plates, including Continental Drift, Seafloor Spreading, and Plate Tectonics.
• Seafloor Spreading Theory states that the seafloor is continually spreading, with new crust formed at oceanic ridges and older crust being recycled into the mantle.
• The discovery of seafloor spreading was supported by new evidence obtained using sonar technology, which allowed scientists to map the ocean floor and identify features like trenches, canyons, and volcanic sea mountains.
• Harry Hammond Hess, a geologist from Princeton University, contributed significantly to the theory of seafloor spreading.
• He observed that the ocean floor was not as smooth as previously thought and discovered the presence of mid-ocean ridges, suggesting that new crust was being formed at these locations.