Understanding Oceanic Crust and Ophiolites

The lecture covers the study of oceanic crust, focusing on methods like direct sampling, geophysical evidence, and geological sampling through ophiolites. It explains the mineralogy of oceanic crust, including olivine, pyroxene, and plagioclase, and discusses the structure and differentiation of oceanic crust layers. The session concludes with a Q&A.

Which method of studying oceanic crust involves scraping a bucket along the ocean floor?

• Dredging

• Drilling

• Bathymetry

• Seismic refraction

What is the primary advantage of studying ophiolites?

• They are found in all oceanic regions.

• They are less expensive to study than other methods.

• They provide a direct view of oceanic crust layers.

• They are easy to access in the ocean.

Which mineral is known for its high magnesium content and curving cracks?

• Olivine

• Plagioclase

• Clinopyroxene

• Orthopyroxene

Which mineral is commonly found in both olivine and pyroxene?

• Iron

• Aluminum

• Calcium

• Nickel

What is the main difference between orthopyroxene and clinopyroxene?

• Color

• Cleavage angle

• Presence of calcium

• Magnesium content

What is the main characteristic of pillow basalts?

• They are found only in continental regions.

• They cool rapidly and form glassy structures.

• They are formed in explosive eruptions.

• They have a high viscosity.

What type of rock is a dolerite?

• An extrusive basalt

• An intrusive basalt

• A type of gabbro

• A type of andesite

What is the significance of ultramafic cumulates in oceanic crust?

• They are the primary source of oceanic sediments.

• They are only found in continental crust.

• They represent the crystallization products of mantle melts.

• They are identical to mantle rocks.

What process is responsible for the formation of depleted harzburgite?

• Sedimentation

• Partial melting

• Metamorphism

• Weathering

What is the primary challenge in studying igneous rocks?

• They are only found in deep oceanic regions.

• They do not preserve original melt compositions.

• They are too rare to find.

• They are too small to analyze.