Magma Formation, Transport, and Volcanic Processes
Magma Formation and Volcanic Processes
Mid-Ocean Ridges
Thinning of lithosphere due to slab pull forces from the denser and older subducting slab. Adiabatic decompression drives melting of the mantle. Production of primitive basalt (~50% SiO2) called Mid-Ocean Ridge Basalt, or MORB. Volcanism is generally effusive (not explosive), producing voluminous basaltic lava flows and pillow lavas.
Continental Rifts
Melting due to thinning of the lithosphere, decompression-driven. More alkaline basalt than MORB
Read MorePlate Tectonics: Convergence, Subduction, and Dynamics
Plate Convergence and Subduction Zones
Oceanic-Oceanic Plate Convergence
Occurs when the oceanic lithosphere cools and thickens as it moves away from the ridge. Eventually, it breaks and subducts.
Characteristics of subduction zones:
- Great bow.
- Intense magmatism, resulting in a string of volcanic islands on the overriding plate.
- Tectonic erosion.
- Melting of the oceanic crust as it enters the sub-lithospheric mantle.
- The overriding plate experiences relatively low pressure, which means:
- Sediments are subducted
Understanding Chemical Equations: Balancing, Types, and Calculations
Understanding Chemical Equations
The Matmata method of equalization in chemical equations involves ensuring that the number of atoms of each element is equal on both sides of the equation.
Methods for Balancing Chemical Equations
The method involves testing coefficients for the elements involved. This begins by adjusting coefficients for elements involved in the compounds.
Types of Chemical Reactions
- Decomposition or Chemical Analysis: AB → A + B
- Synthesis: A + B → AB
- Displacement or Replacement: AB
Understanding Plate Tectonics: Benioff Zones, Continental Drift, and More
Understanding Plate Tectonics
Benioff Zones
The Benioff zone is a seismic area along the Pacific coast of North America, organized in a specific way. Earthquakes originate at varying depths, with shallower events occurring near the coast and deeper events further inland, forming an inclined plane. This plane is referred to as the Benioff surface.
Ocean Floor Dynamics
Area
Openings of only a few millimeters are observed. Seismic analysis indicates that not only the crust is moving, but the entire Lithosphere
Read MoreUnderstanding Map Symbols: Scale, Contours, and Climograms
Understanding Map Symbols
Scale
The scale is the mathematical relationship between real-world dimensions and their representation on a map or plan. For example, a scale of 1/500 indicates the relationship between the graphic size (on paper) and the actual dimensions on the ground.
Contour Lines
A contour line connects points of equal elevation on a map. Contour lines are often printed in sienna for land features and blue for glaciers, deep sea areas, and lakes. A contour line (also called an isopleth,
Read MoreUnderstanding Earth’s Interior: Seismic and Geochemical Methods
The Seismic Method
The seismic method is an indirect method of study that looks at the variations in propagation speed of seismic waves as they travel through different materials inside the geosphere.
Seismic Waves
Seismic waves are vibrations generated inside the Earth at the point where an earthquake takes place. They propagate in all directions, and the more rigid the material they pass through, the more quickly they travel.
Types of Seismic Waves
- P Waves: Cause the material to vibrate, alternating