Earth Science: Plate Tectonics and Layers

Plate Tectonics

• Plate tectonics is the theory that Earth's solid crust is broken into fragments that are slowly and constantly moving over the top of Earth's liquid mantle.
• The theory of plate tectonics was derived from the Greek word "tektonikós", meaning "pertaining to building".
• This refers to the structure and properties of the Earth's crust and its changes over time.

Earth's Layers

• The Earth is composed of layers at different depths due to different densities.
• The deepest layer is the core, which is made of very dense radioactive metal.
• The core has an outer liquid layer and an inner solid layer
• The Earth also consists of the crust, mantle, asthenosphere, outer and inner core.

Heat and Density

• When a substance is heated, it becomes less dense.
• As energy is added, molecules move faster, spread out, and make the area less dense, resulting in fewer molecules per unit of volume.

Chemosynthesis

• Some organisms, such as those found in magma-seeping areas, derive energy from chemicals.
• Chemosynthesis is the process of using chemical energy from various sources to produce food from simple inorganic molecules.
• These organisms are categorized as producers or autotrophs, meaning they produce their own food.

Energy Sources in Earth

• The Earth has two primary energy sources: external (the sun) and internal (radioactive decay in the core).
• Chemical reactions deep within the Earth's crust are responsible for the Earth's internal heat.

Convection Currents

• Convection currents cause movement.
• These currents are observed in heated liquids and occur because heated particles rise, cool, and sink, creating circular patterns of movement.
• Convection currents in the mantle cause plate movement.

Plate Boundaries and Interactions

• Interactions between the solid lithosphere and liquid-like asthenosphere create Earth's geographical features.
• The lithosphere is the crust and the upper mantle.
• The asthenosphere is the softer, more deformable part of the mantle.
• Types of plate interaction include convergent, divergent and transform boundaries.

Three Types of Plate Boundaries

• Divergent: Plates move apart, pulling apart to create new crust. Examples include mid-ocean ridges and continental rifts.
• Convergent: Plates collide, leading to mountain building or subduction (one plate sinking beneath another). Examples include ocean trenches, volcanic arcs, and mountain ranges (i.e., the Himalayas).
• Transform: Plates slide past each other. These boundaries often associate with faults. Examples include the San Andreas Fault.

What happens at Divergent Plate Boundary?

• Plates spread apart in two ways: Seafloor spreading in the ocean and Continental Rifts on the land.

What happens at Convergent Plate Boundary?

• Oceanic-Continental: Denser oceanic crust sinks below less dense continental crust. This can cause volcanoes and mountain ranges.
• Oceanic-Oceanic: Denser oceanic crust sinks below less dense oceanic crust. This can cause trenches and volcanic island arcs.
• Continental-Continental: Two continental plates collide, creating enormous mountain ranges (e.g., Himalayas).

What happens at Transform Plate Boundary?

• Plates slide past each other, resulting in friction, earthquakes, and fractures in the Earth.

Ecology Connection

• Plate tectonics influence biome identity (climate) and population dynamics (migration, competition).
• The distribution of organisms can be affected by the movement of landmasses over time due to plate tectonics.