Question

If the area of the oceanic crust is \(3.2 \times\) \(10^{8} \mathrm{~km}^{2}\) and new seafloor is now being created at the rate of \(2.8 \mathrm{~km}^{2} \mathrm{yr}^{-1}\), what is the mean age of the oceanic crust? Assume that the rate of seafloor creation has been constant in the past.

Short answer

The mean age of the oceanic crust is approximately \(1.14 \times 10^8\) years.

Step-by-step solution

Understand the Given Data

We need to find the mean age of the oceanic crust given its total area and the rate at which new seafloor is being created: - Total area of the oceanic crust: \(3.2 \times 10^8 \ \mathrm{km}^2\)- Rate of seafloor creation: \(2.8 \ \mathrm{km}^2/\mathrm{year}\)Assume that the creation rate has been constant.

Set Up the Relationship

The mean age of the oceanic crust can be found by dividing the total area of the crust by the rate of seafloor creation. The equation we will use is: \[\text{Mean Age} = \frac{\text{Total Area of Oceanic Crust}}{\text{Rate of Seafloor Creation}}\]

Plug In the Values

Substitute the given values into the equation:\[\text{Mean Age} = \frac{3.2 \times 10^8 \ \mathrm{km}^2}{2.8 \ \mathrm{km}^2/\mathrm{year}}\]

Perform the Calculation

Now perform the division to find the mean age:\[\text{Mean Age} = \frac{3.2 \times 10^8}{2.8} = 1.142857 \times 10^8 \approx 1.14 \times 10^8 \ \text{years}\]

Interpret the Result

The mean age of the oceanic crust is approximately \(1.14 \times 10^8\) years, indicating the average time it takes for the oceanic crust to be cycled completely given the current rate of seafloor creation.

Key concepts

Seafloor Spreading

Seafloor spreading is a geological process that happens at mid-ocean ridges. These underwater mountain ranges form along divergent tectonic plate boundaries. In these areas, tectonic plates are moving away from each other, allowing magma from below the Earth's surface to rise and form new oceanic crust. This process gradually pushes the older crust away from the ridge.

• Seafloor spreading occurs continuously, adding more material to the Earth's crust.
• As the new crust forms, it records the Earth's magnetic field at the time of creation, which can provide information about historical geomagnetic reversals.
• Mid-ocean ridges are the most geologically active regions on Earth due to constant volcanic activity and earthquakes.

Seafloor spreading is a critical component of plate tectonics. It helps explain the movement of continents and the distribution of earthquakes and volcanoes. By studying the patterns and rates of seafloor spreading, geologists can understand more about the Earth's evolving landscape.

Mean Age Calculation

Calculating the mean age of the oceanic crust involves determining the average time it takes for the crust to be replaced, given the current rate of seafloor creation. This is an essential measure for understanding the dynamics of ocean crust turnover and geodynamics.To find the mean age, we use the equation:
\[\text{Mean Age} = \frac{\text{Total Area of Oceanic Crust}}{\text{Rate of Seafloor Creation}}\]This equation tells us how much time, on average, it takes for new crust to replace all existing oceanic crust.

• The total area of the oceanic crust is the expanse of the seafloor across the globe. For our problem, this is given as \(3.2 \times 10^{8} \mathrm{~km}^{2}\).
• The rate at which seafloor is created is typically measured per year (in our example, this is \(2.8 \mathrm{~km}^{2}/\mathrm{year}\)).
• From our calculation, the mean age turns out to be approximately \(1.14 \times 10^{8}\) years, indicating how long it takes on average for oceanic crust to cycle through renewal processes completely.

Geodynamics

Geodynamics is the broad scientific study of the forces and processes that shape the Earth's structure. It encompasses everything from the movement of tectonic plates to volcanic activity and earthquakes.
One major aspect of geodynamics is understanding how the Earth's interior processes, like mantle convection, drive the movement of tectonic plates. The energy from these processes leads to phenomena such as seafloor spreading, continental drift, and mountain building.

• This field helps us predict geological events and understand the Earth's past landscape changes.
• It involves studying the Earth’s heat distribution, material properties, and stress fields.
• Tools like GPS technology and remote sensing have advanced our understanding of geodynamics significantly.

By integrating these studies, geodynamics provides a comprehensive view of how the Earth's surface is continually shaped and reshaped over time.