Igneous Rocks Identification Quiz

Continental Drift and Plate Tectonics

• Alfred Wegener, a German atmospheric scientist, developed the idea of Pangea and the slow separation of continents.
• Wegener had no idea of how continental drift occurred.
• "Jock" Tuzo-Wilson developed the mechanism theory for how continental drift works, and called it plate tectonics.

Plate Tectonics

• Continents are the outer layer of the Earth's crust that moves on the semi-fluid layer called the mantle.
• The mantle is constantly shifting, rising, and falling.
• Plates often collide with each other, forming mountains, and move away from each other, creating continental rifts.
• Continental rifts are areas where the continent is extended as the plates move away from each other.

First World Atlas

• Abraham Ortelius, a Finnish cartographer, created the first world atlas in the late 16th century.
• The atlas was released during a time of economic and globalization revolution.
• Traders from Europe wanted to develop the most efficient trade route, which led to the discovery of similarities between the South American and African coastlines.

Sir Francis Bacon

• Sir Francis Bacon, a naturalist and geologist, described the pattern of "fitting" as a result of the biblical flood.
• Bacon believed that erosion was hollowing out the channel, creating the similar coastlines.

Japan and Earthquakes

• Japan is located on the boundary of four different plates: the Philippian plate, Pacific plate, Eurasian plate, and the Okhotsk plate.
• Japan set up a system of seismographs after the Nobi Earthquake in 1891 to record earthquake activity.
• The Nobi earthquake resulted in a 6m fault scarp.

Seismographs

• A seismograph consists of a weight with a pen attached to a spring that records the movement of the ground during an earthquake.
• Earthquakes are measured using two different methods: the Richter Scale and moment magnitude.
• The Richter Scale is a logarithmic scale based on the amplitude of deflection on a seismograph.
• Moment magnitude is based on the actual energy released during an earthquake.

Seismic Waves

• There are two types of seismic waves: body waves and surface waves.
• Body waves move through the body of the Earth, while surface waves are destructive on the surface but don't move through the Earth.
• There are two types of body waves: primary (P) and secondary (S) waves.

Igneous Rocks

• Texture tells us how quickly the magma cooled, with intrusive igneous rocks cooling much slower than extrusive.
• Chemical composition tells us the amount of silica present in a rock, with felsic rocks having high silica levels, intermediate rocks having mid silica levels, and mafic rocks having low silica levels.

Wilson Cycle

• The Wilson Cycle is the process of the breaking up of a continent or a supercontinent by rifting, forming an embryonic ocean.
• Stage 1: A continent undergoes extension, the crust is thinned, and a rift valley forms.
• Stage 2: The continent tears in two, its edges are faulted and uplifted, and basalt eruptions form oceanic crust.
• Stage 3: Continental sediments blanket the subsiding "passive" margins to form continental shelves, and a mid-oceanic ridge develops.

Subduction and Continental Shelves

• Subduction of oceanic crust often results in the crumbling or subduction of continental shelves.
• New oceans initially form above hot spots, which can cause volcanic ash to accumulate and encompass fossils and archeological finds.
• Continental shelves contain most of the world's oil, gas, and marine life.

The Dead Sea Rift

• The Dead Sea Rift is a transform plate boundary between the faster moving Arabian and the African Plate.
• The upward movement of the Arabian plate is causing the Anatolian plate to move west along the North Anatolian Fault.
• The Dead Sea has lots of water entering it but no water leaving, resulting in a very salty lake.

North Anatolian Fault

• The North Anatolian Fault is a transform/strike slip fault.
• Istanbul is based on the fault line, consisting of old masonry buildings (rigid).
• The fault line has cascading earthquakes, with one earthquake occurring and several years later repeating down the transform fault again.

Mature Ocean Basins

• Studying mid-oceanic ridges and sea floor spreading is challenging due to the 2.5 km of water above.
• Magma fills the crater, forming a small mountain, called a tuya, Moberg mountain.
• Hyaloclastites are rocks formed when lava erupts under shallow water, causing it to shatter and cool in fragments.

Volcanic Eruptions

• The Lakagigar (1783) eruption caused the depletion of 50% of Iceland's livestock and 69% of the human population, as well as the destruction of 21 villages.
• The aerosol plume of volcanic ash and gases migrated over southern Europe, leading to crop failure and famine.

Tephra and Volcanic Ash

• Tephra is anything that is thrown out of a volcano, including volcanic ash and volcanic bombs.
• Planes cannot travel through volcanic ash as it can damage turbines and sandblast windshields.

Reykjavik and Hydrothermal Energy

• Reykjavik, the capital city of Iceland, runs on hydrothermal or thermal energy.
• This is done by pumping up hot water from fissures and converting the heat into energy.
• None of this water can be used as a water source directly as it is highly mineralized.

Wilson Cycle and Ophiolites

• The Wilson Cycle is the cycle of the opening and closing of ocean basins.
• When an ocean closes, slivers of the ocean floor are thrust up onto the surface of continents, forming ophiolites.

Test your knowledge on identifying igneous rocks based on their texture and chemical composition. Learn about the characteristics of phaneritic and aphaneritic rocks, as well as the relationship between silica levels and rock viscosity.