Geology Exam Question 2
C. Indicate and explain where igneous rock is being formed, what conditions are allowing magma to be generated in this setting, and where volcanoes would form.
-Decompression Melting : When the earth's mantle moves upward in the area of lower pressure, usually a divergent boundary -Plate separation → Lowered Pressure Lowered pressure causes melting as solid hot mantle rock moves upward -When mantle is effected by constant high temperature causing it to rise → lose temperature and melts -Asthenosphere right up to the surface -Material from mantle loses pressure, crosses past melting point and melts -Molten mafic lava -The lava crystalizes → igneous rocks *VOLCANOES FORM OUTSIDE OF THE RIFT ZONE
D. Explain what composition of rock is originally melted, what types of igneous rock is erupted, and what processes create these final compositions.
-Original composition of melted rock: Mafic -Mafic igneous rock is erupted and created
2. Consider a continental rift zone where a rift valley has formed. Magmatic activity is active, but oceanic crust has not yet formed. Create a concept sketch of this type of tectonic environment and explain and annotate the sketch with the following features/processes:
Divergent Plate Boundary : A boundary with 2 tectonic plates moving apart more info: -Rifts and rift valleys are created -Tensional -Volcanoes -Shallow Earthquakes -Epicenter can only go at the boundaries of ocean and continental crust Decompression Melting
F. Within that setting, where would metamorphism occur (indicate this on your diagram)?
Will occur in the lithosphere near the rift valley.
G. What will most likely happen to a rift valley setting over the next 100 million years? Sketch what the same area will look like after that time, assuming that plate motion remains relatively constant over that time period.
Continue to build new crust and move islands and continental plates.
b. Indicate (with arrows) and explain the direction of stress acting on this region. What types of structural features would you find to indicate this? How would those features be oriented and distributed in the area?
Tensional stress Extensional Forces Faults are created due to the magma's heat and extensional forces → the release of energy creates low magnitude earthquakes Mid Ocean Ridges : Location of rising magma that solidifies into new oceanic crust Zone extension Earthquakes are generating along faults
A. Include the appropriate thickness and location of lithosphere and asthenosphere and label them.
(DO WE NEED EXACT DEPTHS?)
E. Explain and sketch the type of volcano most likely to be found in this setting, and why. Note whether the eruption style is likely to be effusive or explosive, and explain why.
*Shield Volcanoes -Mafic -Low Viscosity -Low Explosively -Large (Biggest) (Sketch on google doc)