Understanding Hawaiian Volcanism and Basalt Types

The lecture covers Hawaiian volcanism, focusing on mantle plumes and basalt types. It explains the stages of Hawaiian volcanic activity, the characteristics of alkali basalts, and the basalt tetrahedron. The discussion includes phase diagrams, silica saturation, and melting experiments, highlighting the dynamics of mantle plumes and their impact on volcanic formations.

What is the primary cause of the systematic changes in Hawaiian volcanic activity?

• The seasonal changes in ocean temperature

• The movement of the Pacific Plate over a stationary mantle plume

• The rotation of the Earth

• The gravitational pull of the moon

Which type of basalt is characterized by high concentrations of alkali metals compared to silica?

• Tholiitic basalt

• Diorite

• Alkali basalt

• Granite

What is a key feature of alkali basalts in terms of mineral composition?

• Abundance of olivine

• Presence of feldspathoids

• Rich in calcium

• High quartz content

What prevents the transition between alkali and tholiitic magmas during crystallization?

• The presence of water

• The pressure of the surrounding rock

• The age of the magma

• The thermal divide

What is the basalt tetrahedron used for?

• Measuring the temperature of lava

• Representing all types of basalts

• Calculating the age of volcanic rocks

• Predicting volcanic eruptions

Which plane in the basalt tetrahedron separates silica under-saturated from silica-saturated basalts?

• Critical plane of silica under-saturation

• Olivine-plagioclase plane

• Quartz-feldspathoid plane

• Thermal divide plane

What type of basalt is formed at high pressures and low degrees of melting?

• Granite

• Olivine tholeiite

• Quartz tholeiite

• Alkali basalt

How does the degree of melting affect the concentration of incompatible elements in basalts?

• Higher degrees of melting increase incompatible elements

• Lower degrees of melting increase incompatible elements

• Incompatible elements are unaffected by melting

• Incompatible elements decrease with lower pressure

What is the relationship between plume temperature and basalt type in Hawaiian volcanism?

• Temperature has no effect on basalt type

• Higher temperatures produce more tholiitic basalts

• Lower temperatures produce more tholiitic basalts

• Higher temperatures produce more alkali basalts

What is the primary factor that influences the type of basalt formed in mantle melting?

• The pressure and degree of melting

• The depth of the ocean

• The age of the volcanic rock

• The color of the magma