The temperature of the Earth’s crust changes depending on depth, location, and geological activity. In general, it follows a pattern known as the geothermal gradient, which is the rate at which temperature increases with depth. Here’s a more detailed breakdown:
1. Near the Earth’s Surface (0-10 km)
At or near the surface, the temperature of the Earth’s crust is primarily influenced by the climate, so it can be similar to the ambient temperature. For example:
- At sea level, the temperature typically ranges from 50-60°F (10-15°C), though this varies depending on the local climate.
- As you go deeper into the crust, the temperature rises. On average, the temperature increases by about 1.5–3°F (0.8–1.6°C) per 100 feet (about 30 meters) of depth. This is known as the geothermal gradient.
2. Deeper in the Crust (10-30 km)
As we move deeper into the Earth, the geothermal gradient continues to increase. By 10 km (6 miles) down, temperatures can reach:
- Around 500°F–700°F (260°C–370°C).
At around 30 km depth (18.6 miles), temperatures can range between:
- 1,200°F–1,600°F (650°C–870°C).
3. Lower Crust (30-60 km)
The temperature continues to rise as we go deeper into the Earth’s crust. By the time you reach depths of 30-60 km (18.6-37.2 miles), the temperature can be anywhere from:
- 1,800°F–2,200°F (980°C–1,200°C).
4. Upper Mantle (60-700 km)
As we transition from the crust into the upper mantle, the temperature becomes much hotter. The Mohorovičić discontinuity (Moho) marks the boundary between the Earth’s crust and the mantle, typically around 35 km (21.7 miles) beneath the surface, although it can vary.
- Temperatures here range from 2,200°F–3,600°F (1,200°C–2,000°C).
5. Magma Chambers and Volcanic Areas
In regions where volcanic activity is prominent, such as near tectonic plate boundaries, hotspots, or subduction zones, the crust can become significantly hotter due to the presence of molten rock or magma below the surface. In these areas, temperatures can exceed:
- 1,800°F–3,200°F (1,000°C–1,760°C).
For example, in areas with active volcanoes, such as around the Pacific Ring of Fire, magma chambers can have temperatures up to 2,200°F (1,200°C) or higher.
6. Core of the Earth (Below the Crust)
Although not part of the crust itself, it’s useful to mention the temperature of the Earth’s core, which significantly impacts the behavior of the surrounding crust. The outer core is liquid and reaches temperatures between:
- 7,200°F–9,000°F (4,000°C–5,000°C), while the inner core can be as hot as:
- 9,500°F–12,000°F (5,300°C–6,700°C).
Factors Influencing Crust Temperature:
- Geothermal Gradient: This is the rate at which temperature increases with depth and can vary by region. For instance, in regions with high volcanic activity or tectonic plate movements, the gradient can be steeper, meaning the temperature increases more rapidly with depth.
- Local Geological Activity: Volcanic regions, geothermal hotspots, and areas with significant tectonic activity tend to have higher crust temperatures.
- Rock Composition: The type of rock in the crust also influences temperature. For example, areas with more radioactive decay (like those with uranium-rich rocks) can generate more heat.