The rim...
The fossils found at the top of a canyon will probably be younger than those at the of the bottom of the canyon because the fossils at the bottom of the canyon would have been there earlier when the so called "canyon" was once a flat land, so as time went by, the flat land began growing and getting taller and finally became a canyon so the fossils at the top of the canyon WOULD be younger than those at the bottom because the bottom fossils were there before the top of the canton even existed.
They climbed to the top of the canyon.
There are sea fossils at the top of the canyon from the seas that once covered the low plains there.
winter in the grand canyon
There is a Chevelon Canyon and Chevelon Lake in Arizona. It is a hiking destination.
The rock formations at the bottom are older.
There are two reasons why the lodging to the Grand Canyon is found at the top. First and foremost, it is logistically more convenient as more tourists visit the top than the bottom. Additionally, in the summer months, the bottom of the canyon can be much more warm in temperature, which could be dangerous for employees and/or lodgers.
The Colorado River could be called the Grand Canyon's mother.
A Canyon, probably
It could be called a gorge.
A deep valley could be called a canyon, such as the Grand Canyon.