The main differences between oceanic and continental lithosphere lie in their thickness, composition, age, density, and thermal properties.
Key Distinctions
Here's a breakdown of the key differences between oceanic and continental lithosphere:
Thickness
- Oceanic Lithosphere: Typically thinner, ranging from 50-100 km.
- Continental Lithosphere: Significantly thicker, ranging from 150-200 km or more.
Composition
- Oceanic Lithosphere: Primarily composed of basalt and gabbro, which are mafic (rich in magnesium and iron) igneous rocks.
- Continental Lithosphere: Composed of a wide variety of rocks, including granite, sedimentary rocks, and metamorphic rocks. The crust is felsic (rich in feldspar and silica). The continental crust is also enriched in radioactive elements like uranium, thorium, and potassium.
Age
- Oceanic Lithosphere: Relatively young, with the oldest parts being around 200 million years old. Oceanic lithosphere is continuously created at mid-ocean ridges and destroyed at subduction zones.
- Continental Lithosphere: Much older, with some regions dating back billions of years. Continents are relatively stable and less prone to destruction.
Density
- Oceanic Lithosphere: Denser than continental lithosphere due to its mafic composition.
- Continental Lithosphere: Less dense than oceanic lithosphere due to its felsic composition.
Subduction
- Oceanic Lithosphere: Subducts beneath continental or other oceanic lithosphere due to its higher density.
- Continental Lithosphere: Does not subduct because it is too buoyant. Collisions between continental plates result in mountain building.
Heat Flow
- Oceanic Lithosphere: Experiences higher heat flow, particularly near mid-ocean ridges.
- Continental Lithosphere: Exhibits lower heat flow due to its thickness and insulating properties.
Summary Table
| Feature | Oceanic Lithosphere | Continental Lithosphere |
|---|---|---|
| Thickness | 50-100 km | 150-200+ km |
| Composition | Basalt, Gabbro (Mafic) | Granite, Sedimentary, Metamorphic (Felsic) |
| Age | <200 million years | Billions of years |
| Density | Higher | Lower |
| Subduction | Yes | No |
| Heat Flow | Higher | Lower |
In summary, the continental lithosphere is thicker, less dense, older, and richer in radioactive elements than its oceanic counterpart, which directly impacts its heat flow and prevents it from subducting.
