How internal forces may have changed the surface of what is now north America over past 225 million years?

Internal forces, including plate tectonics and volcanic activity have significantly shaped the surface of what is now North America over the past 225 million years. These processes have created, modified and destroyed various landscapes, resulting in the continent's current topography and geology.

1. Plate tectonics:

Plate tectonics, the movement and interactions of Earth's tectonic plates, has played a crucial role in reshaping North America.

- Collision and Orogeny: The collision of the North American plate with other tectonic plates over time led to the formation of mountain ranges. For instance, the collision with the Pacific plate gave rise to the Rocky mountains in the west and the Appalachian mountains in the east.

- Rifting: Rifting, the process where plates move apart, also influenced North America's landscape. Most notably, the separation of North America and Africa during the Jurassic Period created the Atlantic ocean and the associated features, such as the Appalachian mountains.

- Subduction: Subduction, where one plate moves beneath another, lead to the formation of volcanic arcs. The subduction of the oceanic Farallon plate beneath the North American plate resulted in volcanic activity and the development of the Sierra Nevada mountains and Cascade Range.

2. Volcanic Activity:

Volcanic activity, associated with plate movements, has further reshaped North America's surface.

- Hotspots: Volcanic hotspots, stationary plumes of magma rising from deep within the Earth, have created volcanic features like the Hawaiian Islands and Yellowstone National Park's geothermal wonders.

- Flood Basalts: Large-scale volcanic eruptions, known as flood basalts, occurred in several episodes, covering vast areas with lava. The Columbia River Basalt Group in the pacific Northwest is an example of such an event.

3. Erosion and Deposition:

Internal forces often work in conjunction with external processes like erosion and deposition to shape landscapes:

- Glaciations: During ice ages, glaciers covered substantial portions of North America. Their movement eroded the landscape, creating features such as fjords, cirques, and moraines. The retreat of these glaciers deposited enormous amounts of sediment, forming moraines and outwash plains.

- River Systems: Rivers and streams have carved valleys, canyons, and deltas over millions of years, shaping the topography and influencing sediment deposition.

In summary, the dynamic interplay of plate tectonics, volcanic activity, and subsequent erosion and deposition has profoundly transformed the surface of North America over the past 225 million years. These processes continue to reshape the continent's landscapes, shaping its physical features and ecosystems.