Final answer:
The Appalachian Mountains and the Rocky Mountains are the areas among the provided options that have the highest landslide material due to their steep slopes, tectonic history, and presence of weak or fractured materials.
Step-by-step explanation:
Landslide Material Distribution
The areas with the highest landslide material are not uniform across the United States but are influenced by various geological factors including the type of rock, slope steepness, and the history of tectonic events. Based on the information provided, the regions that are particularly susceptible to landslides are those with steep topography, weak or fractured materials, and significant tectonic activity. Therefore, among the options provided:
- The Appalachian Mountains, with their long history of tectonic events and steep slopes, are known to have severe landslide problems.
- The Rocky Mountains, being a major mountain range with steep slopes and areas of weak materials, are also prone to landslides.
Other areas like the Florida and the Atlantic Coastal Plains may experience land area loss due to their gently sloping coastlines, but they are not traditionally associated with the highest landslide materials when compared to mountainous regions. The Gulf Coastal Plain also typically has a flatter topography which is less prone to landslide events.