Question 25b. Calculate the full spreading center for: Buenos Aires \( \left(35^{\circ} \mathrm{S}\right. \) latitude) ( 4000 km away from the Mid-Atlantic Ridge)

To calculate the **full spreading rate** at the Mid-Atlantic Ridge based on the location of Buenos Aires, which is situated at **35° S latitude** and **4,000 km away** from the ridge, you can follow these steps: ### **Understanding the Concepts** 1. **Mid-Ocean Ridge and Spreading Centers:** - The Mid-Atlantic Ridge is a **divergent tectonic plate boundary** where the Eurasian and North American plates (in the North Atlantic) and the South American and African plates (in the South Atlantic) are moving away from each other. - **Spreading rate** refers to the speed at which two tectonic plates are moving apart at a mid-ocean ridge. 2. **Full Spreading Rate:** - The **full spreading rate** considers the movement of **both plates away** from the ridge. Therefore, if each plate moves at a rate of *v*, the full spreading rate is **2v**. ### **Calculating the Spreading Rate** To calculate the spreading rate, you'll need two primary pieces of information: - **Distance from the Ridge (D):** 4,000 km - **Age of the Seafloor (T):** This is the time since the seafloor at Buenos Aires' location was formed at the ridge. *Note: If the age isn't provided, it must be estimated or obtained from geological data.* The formula to calculate the **full spreading rate** is: \[ \text{Full Spreading Rate (V)} = \frac{D}{2T} \] Where: - \( D \) = Distance from the ridge (in kilometers) - \( T \) = Age of the seafloor (in millions of years, Ma) ### **Step-by-Step Calculation** 1. **Determine the Age of the Seafloor (T):** - If the age is not provided, geological studies or magnetic anomaly data can help estimate it. - *For example purposes*, let's assume the seafloor is **100 million years (100 Ma)** old. 2. **Apply the Formula:** \[ V = \frac{4,\!000 \text{ km}}{2 \times 100 \text{ Ma}} = \frac{4,\!000 \text{ km}}{200 \text{ Ma}} = 20 \text{ km/Ma} \] 3. **Convert to Common Units:** - **Kilometers per Million Years (km/Ma)** to **Centimeters per Year (cm/year):** - \( 20 \text{ km/Ma} = 20 \times 10^5 \text{ cm} / 10^6 \text{ years} = 2 \text{ cm/year} \) ### **Final Answer:** Given the assumptions: - **Distance from Ridge (D):** 4,000 km - **Age of Seafloor (T):** 100 Ma \[ \text{Full Spreading Rate (V)} = 2 \text{ cm/year} \] ### **Important Considerations:** - **Age Estimation:** The accuracy of the spreading rate heavily depends on the accurate estimation of the seafloor's age. - **Variability:** Spreading rates can vary along different segments of the Mid-Atlantic Ridge. - **Geological Data:** Utilize geological and geophysical data sources for precise calculations. If you have access to the specific age of the seafloor at Buenos Aires' location, substitute that value into the formula to obtain a more accurate spreading rate.