Question

A(n) ________________________ at the Mid-Ocean Ridge, where oceanic plates are diverging and magma is generated by partial melting of the mantle. a. ultramafic magma is produced b. mafic magma is produced c. intermediate magma is produced d. felsic magma is produced

Short answer

Mafic magma is produced at the Mid-Ocean Ridge.

Step-by-step solution

Understanding Divergent Boundaries

At the Mid-Ocean Ridge, oceanic plates are moving apart. As these plates diverge, the mantle beneath them partially melts due to the decrease in pressure, a process known as decompression melting. This melted material rises to fill the gap, forming new crust.

Identifying Magma Type Produced

When partial melting of the mantle occurs, it typically results in the production of magma rich in magnesium and iron, the main components of oceanic crust. This type of magma is known as mafic magma, which is characterized by its high density and dark color.

Selecting the Correct Option

Based on the process of magma formation at Mid-Ocean Ridges, the correct option that describes the magma produced is 'b. mafic magma is produced'. Mafic magma is typical in environments where oceanic crust is formed.

Key concepts

Divergent Boundaries

At the core of plate tectonics are divergent boundaries, which are areas where two tectonic plates move apart.
This process is prominently observed at Mid-Ocean Ridges, where new oceanic crust is generated. As the plates drift away from each other, they create a gap that is gradually filled by material rising from the mantle below.
The main characteristic of divergent boundaries is the formation of new crust. This perpetual movement and generation of new material contribute to the expansion of the ocean floor. Other key features include:

• Fissures and cracks form as the plates pull apart.
• Frequent volcanic activity due to the movement of magma.
• Creation of underwater mountain ranges, known as "mid-ocean ridges."

Divergent boundaries play an essential role in the dynamic nature of Earth's surface, continuously shaping the ocean floor in a slow but constant process.

Mafic Magma

When discussing magma types, mafic magma is fundamental in understanding oceanic crust formation. It is produced at divergent boundaries, especially at Mid-Ocean Ridges.
This type of magma is rich in magnesium and iron, which influences its physical properties.
Mafic magma is distinguished by several characteristics:

• High density and a darker color, owing to its mineral content.
• Low viscosity, allowing it to flow more easily than other magma types.
• Responsible for forming basaltic rocks, which are the primary component of the ocean floor.

The generation of mafic magma is a continuous process at mid-ocean ridges, contributing to the ever-growing oceanic crust. By understanding the properties of mafic magma, geologists can better comprehend ongoing geological processes.

Decompression Melting

Decompression melting is a critical process that turns solid mantle material into liquid magma.
It occurs uniquely at divergent boundaries where tectonic plates diverge, resulting in a decrease in pressure on the mantle material beneath the plates.
As pressure decreases, the mantle begins to melt at temperatures it wouldn't under normal conditions. Here are the essential points about decompression melting:

• Triggered by a reduction in pressure rather than an increase in temperature.
• Facilitates the upward movement of magma to create new crust.
• Commonly happens in regions where plates are moving apart, like the Mid-Ocean Ridge.

This process is essential for understanding how new oceanic crust is formed continuously. It explains why magma from the mantle rises to fill the gaps left by diverging plates. Decompression melting is integral to the cycle of crust creation and tectonic activity in Earth's oceans.