SEAFLOOR SPREADING THEORY | HOW TO CALCULATE THE RATE OF SEAFLOOR SPREADING | MAGNETIC REVERSAL

Summary

In this educational video, students learn about the seafloor spreading theory, which explains the movement of tectonic plates. Key concepts include the history of continental drift, the discovery of mid-ocean ridges, and the process of new seafloor formation at these ridges. The video guides students through a simulation activity to visualize seafloor spreading and discusses the evidence supporting the theory, such as magnetic stripes and the age of rocks near the ridges. It also covers the calculation of the rate of seafloor spreading, enhancing understanding of this geological process.

Takeaways

• 🌐 The continental drift theory posits that all continents were once part of a single landmass called Pangaea, which broke apart and drifted to their current positions.
• 🔍 Evidence for continental drift includes the fit of continents, fossil records, rock and mountain range similarities, and coal and glacial deposits.
• 🧐 Alfred Wegener's initial theory of continental drift was not widely accepted due to a lack of explanation for the mechanism of continental movement.
• 🌊 The advancement of technology allowed scientists to map the ocean floor, discovering mid-ocean ridges similar to those on land.
• 🔥 Harry Hess proposed seafloor spreading in the 1960s, suggesting that continental movement is driven by this process.
• 🌋 Seafloor spreading occurs at mid-ocean ridges where new oceanic crust forms as magma rises and solidifies.
• 🧲 The magnetic stripes pattern near mid-ocean ridges, with normal and reverse polarities, is evidence of seafloor spreading.
• 📏 The age of rocks near mid-ocean ridges decreases with distance from the ridge, indicating younger rocks closer to the spreading center.
• ⏱️ The rate of seafloor spreading can be calculated using the distance between magnetic stripes and the time since their formation.
• 🌍 The process of seafloor spreading is integral to understanding the movement of tectonic plates and the evolution of the Earth's continents.

Q & A

What is the concept of 'seafloor spreading' as discussed in the script?

Seafloor spreading is a geological process where new oceanic crust is formed at mid-ocean ridges due to the upwelling of mantle material, which then cools and solidifies. This process causes the seafloor to spread outward as tectonic plates move away from the ridges.

What evidence supports the continental drift theory mentioned in the script?

The evidence supporting continental drift includes the fitting edges of continents, fossil records of prehistoric organisms, similarities in rock and mountain ranges, and the presence of coal and glacial deposits.

Why was Alfred Wegener's idea on continental drift not accepted by his colleagues initially?

Alfred Wegener's idea on continental drift was not accepted because he failed to explain the mechanism by which the continents could move and drift apart.

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

Mid-ocean ridges are underwater mountain ranges found in the middle of the ocean floor. They are related to seafloor spreading as they are the sites where new oceanic crust is formed due to the upwelling of magma from the mantle.

Who proposed the seafloor spreading theory and how does it relate to the movement of continents?

Harry Hammond Hess proposed the seafloor spreading theory in the early 1960s. It relates to the movement of continents by suggesting that the continents move apart as new crust is formed at the mid-ocean ridges, and old crust is consumed at subduction zones.

What materials and tools are needed for the seafloor spreading simulation activity described in the script?

The materials and tools needed for the simulation activity include board paper or a paper folder, long size construction paper, a pencil, pen or colored pencil, a pair of scissors, paste or glue or sketch tape, and a ruler.

What do the stripes in the seafloor spreading simulation represent?

The stripes in the simulation represent the rocks with normal and reverse polarities, which are indicative of the magnetic field's orientation at the time the rocks were formed.

What is the role of the mid-ocean ridges in the movement of lithospheric plates?

The mid-ocean ridges are the origin of the lithospheric movement. They are where the force that pushes the lithospheric plates originates, as new crust is formed and pushes the plates apart.

How does new seafloor form at the mid-ocean ridges?

New seafloor forms at the mid-ocean ridges as hot, less dense material from below the Earth's crust rises towards the ridges. This material flows sideways, creating a crack in the crust where magma flows out, cools down, and becomes new seafloor.

What processes occur at the sides of the mid-ocean ridges?

At the sides of the mid-ocean ridges, the process of seafloor spreading occurs, where new crust is formed. Additionally, the old seafloor is destroyed at subduction zones where one tectonic plate moves under another.

How can the rate of seafloor spreading be calculated using the magnetic field graph?

The rate of seafloor spreading can be calculated by measuring the distance between magnetic stripes on the graph and dividing it by the time represented by those stripes. The rate is then converted from kilometers per million years to centimeters per year using appropriate conversion factors.