Earth's Chemical Layers

Earth's Chemical Layers

• The Earth is composed of three distinct chemical layers: crust, mantle, and core.
• The crust is the outermost layer, composed of two types: continental crust (granitic, low density) and oceanic crust (basaltic, high density).
• The crust is brittle near the surface but becomes more ductile at depth due to increased pressure and temperature.
• The Mohorovičić Discontinuity (Moho) marks the transition between the crust and mantle, characterized by a significant increase in seismic velocity.
• The Moho is located approximately 5 km below the ocean floor and 30-40 km beneath continents, deepening near mountain-building zones.
• The mantle, the largest chemical layer, extends from the base of the crust to a depth of approximately 2900 km.
• It is primarily composed of peridotite, an ultramafic igneous rock.
• Information about the mantle is gathered from seismic wave analysis, ophiolites (pieces of mantle exposed on the ocean floor), and xenoliths (mantle rock transported to the surface within magma).
• The Earth's core, containing both liquid and solid layers, is primarily composed of iron and nickel, with potentially some oxygen.
• The core was first discovered in 1906 through analysis of seismic data.
• Scientists believe the core formed from metallic materials like iron and nickel that sank to the center of the Earth, liquefied by intense pressure.

Earth's Physical Layers

• The Earth can be further divided into five distinct physical layers based on how they respond to stress: lithosphere, asthenosphere, mesosphere, outer core, and inner core.
• The lithosphere is the rigid outermost layer, including the crust and uppermost part of the mantle.
• The asthenosphere is the layer beneath the lithosphere, characterized by partial melting and a ductile, "plastic-like" behavior.
• The mesosphere is the lower part of the mantle, below the asthenosphere, where the mantle is solid but still behaves in a ductile manner.
• The outer core is a liquid layer that resides beneath the mantle, primarily composed of molten iron and nickel.
• The inner core is a solid ball of iron and nickel located at the Earth's center. Even though the inner core experiences extreme temperatures, the intense pressure keeps the material in a solid state.