Grade 11 & 12 | Earth Science | Seafloor spreading | Theresa Reyes Q2 W5

Summary

In this educational video, Teresa Reyes, an Earth Science teacher, explains the geological process of seafloor spreading, a key phenomenon occurring at divergent plate boundaries. The lesson covers the process by which tectonic plates move apart, allowing molten magma to rise and create new oceanic crust at mid-ocean ridges. Key evidence supporting this process includes deep-sea trenches, geomagnetic reversals, and the age of the seafloor. The video also highlights the role of seafloor spreading in shaping Earth's features, such as the creation of the Red Sea, and emphasizes how the balance between seafloor spreading and subduction keeps Earth's dimensions constant.

Takeaways

• 😀 Seafloor spreading occurs at divergent plate boundaries, where tectonic plates slowly move apart.
• 😀 Magma rises from the mantle to create new ocean floor at mid-ocean ridges, forming volcanic landscapes.
• 😀 The ocean crust is part of a conveyor belt system, moving from mid-ocean ridges to deep-sea trenches.
• 😀 The mid-Atlantic Ridge is the longest mountain chain on Earth, representing a slow spreading center of the ocean floor.
• 😀 The East Pacific Rise is a faster spreading center, with a rate of 6 to 16 cm per year.
• 😀 The age, density, and thickness of oceanic crust increase as you move away from the mid-ocean ridge.
• 😀 Deep sea trenches are long, narrow depressions formed by subduction, where older oceanic crust is recycled back into the mantle.
• 😀 Geomagnetic reversals, recorded as alternating magnetic stripes on the ocean floor, provide strong evidence of seafloor spreading.
• 😀 The oldest oceanic crust is around 200 million years old, indicating that the ocean floor is constantly being renewed through seafloor spreading and subduction.
• 😀 Seafloor spreading and subduction balance each other, keeping the shape and diameter of Earth constant over time.
• 😀 The Red Sea formed through seafloor spreading between the African and Arabian plates, and it may eventually connect with the Mediterranean Sea.

Q & A

What is seafloor spreading?

Seafloor spreading is a geologic process in which tectonic plates or large slabs of Earth's lithosphere split apart from each other. This process occurs at divergent plate boundaries, where molten material rises from the mantle, creating new oceanic crust.

Who first proposed the hypothesis of seafloor spreading?

The seafloor spreading hypothesis was first proposed by Princeton geologist Harry Hammond Hess in the early 1960s.

How does seafloor spreading occur?

Seafloor spreading occurs when tectonic plates slowly separate at divergent plate boundaries, allowing molten material from the mantle to rise and create new ocean floor. This new crust then moves away from the ridge towards oceanic trenches, where it is subducted back into the mantle.

What are mid-ocean ridges and how do they relate to seafloor spreading?

Mid-ocean ridges are large mountain chains on the ocean floor, formed at divergent plate boundaries. These ridges are spreading centers where magma rises from the mantle, creating new oceanic crust. For example, the Mid-Atlantic Ridge is a slow spreading center, while the East Pacific Rise is a fast spreading center.

What is the significance of deep-sea trenches in seafloor spreading?

Deep-sea trenches are long, narrow basins formed by the subduction of tectonic plates. They play a crucial role in seafloor spreading as older oceanic crust is pushed beneath lighter plates at these subduction zones, where it is recycled back into the mantle.

What role do geomagnetic reversals play in understanding seafloor spreading?

Geomagnetic reversals provide evidence for seafloor spreading. As basaltic magma cools at mid-ocean ridges, it records the Earth's magnetic field, creating alternating bands of normal and reverse polarity. These magnetic stripes are symmetrical on either side of mid-ocean ridges, supporting the idea of seafloor spreading.

How does the age of the ocean floor provide evidence for seafloor spreading?

The age of the ocean floor shows that the youngest crust is located near mid-ocean ridges, and it becomes progressively older as you move further away from the ridges. This pattern indicates that new ocean floor is created at ridges and older crust is subducted at deep-sea trenches.

How does seafloor spreading contribute to the balance of Earth's crust?

Seafloor spreading creates new oceanic crust at divergent plate boundaries, while subduction destroys old crust at deep-sea trenches. These two processes balance each other, ensuring that the shape and diameter of the Earth remain constant over time.

What is an example of a geographic feature formed by seafloor spreading?

An example of a geographic feature formed by seafloor spreading is the Red Sea. It was created when the African and Arabian plates slowly separated due to seafloor spreading, and geologists predict that it will eventually lead to the complete separation of the Arabian Peninsula from the rest of Africa.

What does the process of subduction involve?

Subduction involves one tectonic plate being pushed beneath another at a convergent boundary. This occurs when an older, denser plate is forced into the mantle, causing the seafloor and outer crust to bend and form steep, v-shaped trenches.