Explain the differences between the continental and oceanic crust.

The continental crust and oceanic crust are two distinct layers that make up the Earth's outermost shell, known as the lithosphere. While they are both part of the Earth's crust, there are several key differences between them.

1. Composition: The continental crust is primarily composed of granitic rocks, which are lighter in color and less dense compared to the oceanic crust. On the other hand, the oceanic crust is mainly composed of basaltic rocks, which are darker and denser.

2. Thickness: The continental crust is significantly thicker than the oceanic crust. On average, the continental crust is about 35-40 kilometers thick, while the oceanic crust is only about 5-10 kilometers thick.

3. Age: The continental crust is generally much older than the oceanic crust. The oldest continental rocks date back to around 4 billion years, while the oldest oceanic rocks are only about 200 million years old.

4. Density: Due to its composition, the continental crust has a lower density compared to the oceanic crust. This lower density allows the continental crust to "float" higher on the denser underlying mantle, forming continents. In contrast, the oceanic crust is denser and sinks beneath the continental crust in a process called subduction.

5. Topography: The continental crust is characterized by diverse topography, including mountains, plateaus, and plains. This variation in topography is due to the thicker and less dense nature of the continental crust. In contrast, the oceanic crust is relatively flat and features underwater mountain ranges known as mid-ocean ridges.

6. Heat Flow: The continental crust has a lower heat flow compared to the oceanic crust. This is because the continental crust is thicker and acts as an insulating layer, preventing heat from the Earth's interior to escape easily. The oceanic crust, being thinner, allows for more efficient heat transfer.

Overall, the continental and oceanic crusts differ in terms of composition, thickness, age, density, topography, and heat flow. These differences play a crucial role in shaping the Earth's surface and influencing various geological processes.