Question

\(10 \mathrm{~km}\) of new seafloor has been created in 50,000 years, with \(5 \mathrm{~km}\) on each side of a mid-ocean ridge. What is the rate of movement, in km per year, of each plate? In cm per year?

Short answer

Each plate moves at 0.0001 km/year or 10 cm/year.

Step-by-step solution

Calculate the total movement of one plate in km

Since the total new seafloor created is 10 km, this means 5 km is added to each side of the mid-ocean ridge over 50,000 years (as given by the problem). Therefore, the total movement for one plate is 5 km.

Calculate the rate in km per year

Divide the movement of one plate by the total time. So, the rate of movement in km per year is \( \frac{5 \text{ km}}{50000 \text{ years}} = 0.0001 \text{ km/year} \).

Convert km per year to cm per year

Since 1 km equals 100,000 cm, convert the rate from km/year to cm/year: \( 0.0001 \text{ km/year} \times 100,000 \text{ cm/km} = 10 \text{ cm/year} \).

Key concepts

Plate Tectonics

Plate tectonics is a scientific theory that explains the large-scale movements of Earth's lithosphere, which is broken into tectonic plates. This theory provides insight into various geological phenomena such as earthquakes, volcano formation, and mountain building. The Earth's outer shell consists of several large and small plates that float on the semi-fluid asthenosphere below. These plates constantly move, interact, and reshape Earth's surface.
One important aspect of plate tectonics is the interaction between plates. There are three main types of plate boundaries:

• Divergent boundaries: Plates move apart, forming new crust through volcanic activity.
• Convergent boundaries: Plates collide, causing one plate to subduct beneath the other.
• Transform boundaries: Plates slide past each other horizontally.

Understanding these movements helps scientists map the formation of continents and oceans, as well as predict potential geological events. As plates move, they can also create a mid-ocean ridge, where new oceanic crust is continuously formed.

Mid-Ocean Ridge

A mid-ocean ridge is an underwater mountain range formed by plate tectonics. It occurs at divergent boundaries where two tectonic plates are moving away from each other. As these plates separate, magma from the mantle rises to fill the gap. This magma cools and solidifies to form new oceanic crust. The continuous process of magma erupting and solidifying leads to the characteristic ridge shape.
The mid-ocean ridge system is the longest mountain range in the world, stretching over 65,000 kilometers across the global ocean floor. Not only does it form new crust, but it also acts as a site for hydrothermal vents. These vents support unique ecosystems, which thrive on the heat and minerals released by these underwater geysers.
The creation of new seafloor at mid-ocean ridges plays a critical role in the seafloor spreading process, pushing tectonic plates apart and leading to the expansion of the ocean basin. This geological feature not only affects the ocean's topography but also helps regulate Earth's heat balance by allowing heat to escape from the mantle.

Rate of Movement

Understanding the rate of tectonic plate movement is essential in geology. It helps scientists determine how quickly or slowly geological features change over time. The rate of movement is usually measured in kilometers or centimeters per year, indicating how much distance a single plate travels over a specific period of time.
In the given exercise, for example, we determine the rate of movement by dividing the total distance a plate moves by the time taken. In this case, with 5 kilometers of movement in 50,000 years, the rate is 0.0001 kilometers per year. To better comprehend the change, we often convert this into a more familiar unit, such as centimeters. With 1 kilometer equating to 100,000 centimeters, this means the plates move at a rate of 10 centimeters per year.
Such measurements are central in studying the dynamics of Earth's surface. By tracking the rates of movement across various locations, geologists can predict future geological phenomena and understand past shifts in the planet's crust. It is fascinating to see how these seemingly small movements lead to significant changes over geological timescales.