It is the Grand Canyon—hopefully you know what it looks like! It consists of a series of generally impassable layers, most of which are sedimentary, like the Coconino Sandstone, Red Wall, and Tonto Platform. But there has been other geological activity too: the Inner Gorge is made of a volcanic schist that has been pierced by granite dikes. The 3 trails involved in RRR are steadily up or down—there are hardly any rolling sections.
The 3 trails are heavily used and well maintained. Some sections are rocky, but usually the footing is smooth. Because mule trains use South Kaibab and Bright Angel, there are extensive water bars to prevent erosion—the trail is sometimes like a long staircase. Expect lots of dust, particularly during dry spells and when foot traffic is heaviest.
The South Rim is dominated by ponderosa pines; on the North Rim you’ll also find scrub oak and aspens. As you descend, you’ll first pass by pinyon pines and juniper trees. Just below is the desert scrub community: creosote, blackbrush, ocotillo, prickly pear, and yucca. And finally, along the Colorado River, it’s a riparian environment, with mesquite trees, willows, and the invasive tamarisk.
Typical of the Southwest, snowfall at the Grand Canyon is erratic, by both yearly and decadal measures. On average, snow begins to fall in November, and earnest melting begins in March. Aftern an average Winter and Spring, expect to encounter snow on the highest, most heavily shaded sections on the South Rim Trails through ~mid-March and on the North Kaibab Trail through ~April.
The South Rim is 4,860 vertical feet above the Colorado River, and the North Rim is 5,850 feet higher. Therefore, you will likely encounter a wide range of temperatures during your trip. For example, if you start early on an April morning from the South Rim, a normal temperature would be in the low-30’s. And if you were in the Inner Gorge during the day’s high temperature, it would likely be in the low-80’s—a 50-degree difference! For more historical weather information, visit http://www.grand.canyon.national-park.com/weather.htm.