CH.1 Earth's Structure and Plate Tectonics: A Comprehensive Study Guide

GEOL 215

What is the Crust?

The Crust is the Earth's outermost layer, which varies in thickness and composition. It is categorized into two main types: oceanic crust, which is thinner and denser, and continental crust, which is thicker and less dense.

What is Oceanic Crust?

Oceanic Crust is the portion of the Earth's crust that underlies the oceans. It is generally denser, thinner, and younger than continental crust, primarily composed of basalt and gabbro, and typically measuring between 5-7 kilometers in thickness.

What is Continental Crust?

Continental Crust forms the landmasses on Earth. It is less dense, thicker, and older than oceanic crust, predominantly composed of granite, and generally ranges from 30 to 40 kilometers in thickness.

What is the Mantle?

The Mantle is the thickest layer of the Earth that lies between the crust and the core. It is composed mainly of peridotite and extends to a depth of approximately 2,900 kilometers.

What is the Upper Mantle?

The Upper Mantle includes both the lithosphere and asthenosphere. It is characterized by partial melting, which allows for the movement of tectonic plates and contributes to geological activity.

What is the Lower Mantle (Mesosphere)?

The Lower Mantle, also known as the Mesosphere, is more rigid than the Upper Mantle. It is characterized by changes in mineral composition due to extremely high pressure and temperature conditions.

What is the Core?

The Core is the Earth's innermost layer, composed primarily of iron and nickel. It is divided into two parts: the outer core and the inner core.

What is the Outer Core?

The Outer Core is the liquid layer of the Earth's core that surrounds the inner core. It is responsible for generating the Earth's magnetic field through the movement of molten iron.

What is the Inner Core?

The Inner Core is the solid innermost layer of the Earth, composed mostly of iron and nickel. It is extremely dense and exists under immense pressure.

What is the Lithosphere?

The Lithosphere is the rigid outermost shell of the Earth, comprising both the crust and the upper mantle. It is broken into tectonic plates that move on the softer asthenosphere beneath.

What is the Asthenosphere?

The Asthenosphere is a partially molten, plastic-like layer of the upper mantle located beneath the lithosphere. Its semi-fluid nature allows tectonic plates to move and shift.

What are Divergent Boundaries?

Divergent Boundaries are tectonic plate boundaries where plates move apart from each other. This process creates new crust, often observed at mid-ocean ridges.

What are Convergent Boundaries?

Convergent Boundaries occur when two tectonic plates collide. This interaction can lead to subduction, where one plate slides beneath another, or the formation of mountain ranges through continental collision.

What are Transform Boundaries?

Transform Boundaries are locations where tectonic plates slide past each other horizontally. These boundaries are often associated with earthquakes due to the friction created during movement.

What are Hotspots?

Hotspots are volcanic regions that experience active volcanism not necessarily linked to tectonic plate boundaries. They are believed to be caused by columns of hot material, known as mantle plumes, rising from deep within the Earth.

What are Mantle Plumes?

Mantle Plumes are vertical columns of hot, molten rock rising from deep within the Earth's mantle. They can create volcanic activity and form volcanic chains as tectonic plates move over them.

What is the Wilson Cycle?

The Wilson Cycle is a geological model that describes the cyclical process of ocean basin formation and closure, explaining the lifecycle of oceans over geological timescales through various tectonic activities.

What are Igneous Rocks?

Igneous Rocks are formed from the cooling and solidification of molten material (magma or lava). Common examples include granite, which is intrusive, and basalt, which is extrusive.

What are Sedimentary Rocks?

Sedimentary Rocks are formed through the accumulation and compaction of sediment particles. They often form in layers and commonly include rocks like sandstone and limestone.

What are Metamorphic Rocks?

Metamorphic Rocks originate from existing rocks that undergo transformation due to extreme heat, pressure, or chemical processes. They can exhibit new textures and mineral compositions.

What is the Moho Discontinuity?

The Moho Discontinuity is the boundary that separates the Earth's crust from the underlying mantle, marking a change in compositional and physical characteristics.

What is the Gutenberg Discontinuity?

The Gutenberg Discontinuity is the boundary that separates the Earth's mantle from the outer core, indicating a significant change in material behavior—from solid to liquid.

What is the Lehman Discontinuity?

The Lehman Discontinuity is the boundary that separates the Earth's outer core from the inner core, marking the transition from liquid to solid state.

What are Subduction Zones?

Subduction Zones are regions where one tectonic plate slides beneath another, typically associated with intense geological activity and the formation of deep ocean trenches and volcanic arcs.

What are Orogenic Belts?

Orogenic Belts are mountain ranges formed through the collision of continental plates. These geological structures are often characterized by diverse rock types and complex geological processes.

What is Seafloor Spreading?

Seafloor Spreading is the geological process occurring at divergent boundaries where new oceanic crust is formed as magma rises from the mantle, creating new ocean floor.