Tim Fitzharris / Grand Tetons from Schwabacher Landing, Grand Teton National Park, Wyoming

Yva Momatiuk & John Eastcott / Canoe on river in summer, Hudson River, Hudson Gorge Wilderness, New York

Jeff Foott / Joshua Tree (Yucca brevifolia) group in desert, Virgin Mountains, Gold Butte National Monument, Nevada

Tim Fitzharris / Marsh, Two Medicine Lake, Glacier National Park, Montana

Tim Fitzharris / Western Juniper (Juniperus occidentalis) and Jeffrey Pine (Pinus jeffreyi) trees, Phipps Peak, Eldorado National Forest, California

Tim Fitzharris / Dana Plateau from Ellery Lake, Sierra Nevada, Inyo National Forest, California

Tim Fitzharris / Dana Plateau from Ellery Lake, Sierra Nevada, Inyo National Forest, California

Tim Fitzharris / Rhododendron (Rhododendron sp) flowers and Coast Redwood (Sequoia sempervirens) trees in fog, Redwood National Park, California

Tim Fitzharris / Half Dome reflecting in Merced River, Yosemite National Park, California

Tim Fitzharris / String Lake and the Grand Tetons, Grand Teton National Park, Wyoming

Tim Fitzharris / River in gorge, Rio Grande Gorge, Rio Grande del Norte National Monument, New Mexico

Yva Momatiuk & John Eastcott / Sand dunes and scattered rocks, Death Valley National Park, California

Yva Momatiuk & John Eastcott / Joshua Tree (Yucca brevifolia) group, Joshua Tree National Park, California

Yva Momatiuk & John Eastcott / Mountain peaks after first snow, Rocky Mountains, Colorado

Yva Momatiuk & John Eastcott / Ripples on white gypsum sand dunes, White Sands National Park, New Mexico

Floris van Breugel / View of snow-like dunes of the White Sands National Park. These sand grains consist of tiny crystals of gypsum. New Mexico, USA, April 2010

Tim Fitzharris / Yosemite Falls, Yosemite National Park, California

Yva Momatiuk & John Eastcott / Snake River and sagebrush prairie, Grand Teton National Park, Wyoming

Yva Momatiuk & John Eastcott / Grand Teton peak with cumulus clouds, Grand Teton National Park, Wyoming

Yva Momatiuk & John Eastcott / Saplings amidst coniferous trees burned by forest fire, Yellowstone National Park, Wyoming

Yva Momatiuk & John Eastcott / Cumulus clouds above the open range, Pryor Mountain, Montana

Tim Fitzharris / Tourists viewing Grand Prismatic Pool, Midway Geyser Basin, Yellowstone National Park, Wyoming

Flip Nicklin / Blue Shark (Prionace glauca) underwater portrait, California

Tim Fitzharris / Colorful clouds against blue sky, New Mexico

Norbert Wu / Blue Rockfish (Sebastes mystinus) schools under kelp forest canopy, Monterey, California

Tim Fitzharris / Mount Rainier and Reflection Lake, Mount Rainier National Park, Washington

Fred Bavendam / West Indian Manatee (Trichechus manatus) eating Hydrilla (Hydrilla sp) an introduced plant that often clogs waterways, Blue Spring State Park, Florida

Tim Fitzharris / Boulders and mountain, Rocky Mountain National Park, Colorado

Tim Fitzharris / Zion Canyon and Virgin River, Zion National Park, Utah

Tim Fitzharris / Conifers in winter, Yellowstone National Park, Wyoming

Yva Momatiuk & John Eastcott / Calcium tufa formations, Mono Lake, California

Yva Momatiuk & John Eastcott / Sandstone hills along lake, Lake Powell, Glen Canyon National Recreation Area, Utah

Yva Momatiuk & John Eastcott / Sandstone formations deeply eroded by water, Spring Valley State Park, Nevada

Yva Momatiuk & John Eastcott / Joshua Tree (Yucca brevifolia) in desert, Eagle Valley Reservoir, Nevada

Yva Momatiuk & John Eastcott / Calcium tufa formations, Mono Lake, California

Yva Momatiuk & John Eastcott / Calcium tufa formations, Mono Lake, California

Yva Momatiuk & John Eastcott / Calcium tufa formations, Mono Lake, California

Yva Momatiuk & John Eastcott / Calcium tufa formations, Mono Lake, California

Yva Momatiuk & John Eastcott / Calcium tufa formations, Mono Lake, California

Yva Momatiuk & John Eastcott / Calcium tufa formations, Mono Lake, California

Yva Momatiuk & John Eastcott / Calcium tufa formations, Mono Lake, California

Yva Momatiuk & John Eastcott / Hillsides along river, Snake River, Idaho

Jeff Foott / Golden Bee Plant (Cleome platycarpa) flowerings, Painted Hills, John Day Fossil Beds National Monument, Oregon

Jeff Foott / Buttes, Grand Staircase-Escalante National Monument, Utah

Jeff Foott / Waterfall in desert, Calf Creek Falls, Grand Staircase-Escalante National Monument, Utah

Jeff Foott / Broken Bow Arch, Grand Staircase-Escalante National Monument, Utah

Jeff Foott / Moqui marble rock formations, Grand Staircase-Escalante National Monument, Utah

Tim Fitzharris / Dana Plateau from Ellery Lake, Sierra Nevada, Inyo National Forest, California

Tim Fitzharris / Moon over peaks, Ritter Range, Sierra Nevada, California

Tim Fitzharris / Moon over peaks, Ritter Range, Sierra Nevada, California

Tim Fitzharris / Lake Mary and Mammoth Crest, Mammoth Lakes, California

Tim Fitzharris / Western Juniper (Juniperus occidentalis) and Jeffrey Pine (Pinus jeffreyi), Phipps Peak, Eldorado National Forest, California

Tim Fitzharris / Green False Hellebore (Veratrum viride) along lake, Dana Plateau, Ellery Lake, Sierra Nevada, Inyo National Forest, California

Tim Fitzharris / Eagle Falls, Eldorado National Forest, California

Daniel J. Cox / Steaming fumaroles, Castle Geyser, Upper Geyser Basin, Yellowstone National Park, Wyoming

Benjamin Olson / Canoe on lake, Superior National Forest, Minnesota

Jeff Foott / Calf Creek Falls, Grand Staircase-Escalante National Monument, Utah

Tim Fitzharris / Ice Plant (Carpobrotus edulis) and flowering Seaside Fleabane (Erigeron glaucus) on coast, Pebble Beach, California

Tim Fitzharris / Monterey Cypress (Cupressus macrocarpa) tree along coast, Pescadero Point, Pebble Beach, California

Tim Fitzharris / Eagle Peak from Mirror Lake, Cascade Range, Lassen Volcanic National Park, California

Tim Fitzharris / Ice Plant (Carpobrotus edulis) flowering along coast, Russian River, California

Tim Fitzharris / Ice Plant (Carpobrotus edulis) and flowering Seaside Fleabane (Erigeron glaucus) on coast, Pebble Beach, California

Tim Fitzharris / Ruby Range, Lost Lake Slough, Colorado

Tim Fitzharris / Hoodoos in winter, Bryce Canyon National Park, Utah

Tim Fitzharris / Hoodoos in winter, Bryce Canyon National Park, Utah

Tim Fitzharris / Rainbow over rock formation called the Three Judges, Goblin Valley State Park, Utah

Tim Fitzharris / Hoodoos in winter, Bryce Canyon National Park, Utah

Tim Fitzharris / Mountain, Capitol Reef National Park, Utah

Tim Fitzharris / Rock formations in winter, Dillon Pinnacles, Curecanti National Recreation Area, Colorado

Tim Fitzharris / Oak (Quercus sp) tree and Indian Blanket (Gaillardia pulchella) flowers, Texas

Tim Fitzharris / Twin Peaks, Twin Lakes, Colorado

Tim Fitzharris / Hallett Peak, Dream Lake, Rocky Mountain National Park, Colorado

Tim Fitzharris / Ruby Range, Lost Lake Slough, Colorado

Tim Fitzharris / Maroon Bells, Maroon Lake, Colorado

Tim Fitzharris / Deer Mountain, Rocky Mountain National Park, Colorado

Tim Fitzharris / Ruby Range, Lost Lake Slough, Colorado

Tim Fitzharris / Ruby Range, Lost Lake Slough, Colorado

Tim Fitzharris / Rock formations, Garden of the Gods, Colorado

Tim Fitzharris / Rock formations in winter, Dillon Pinnacles, Curecanti National Recreation Area, Colorado

Tim Fitzharris / Water in pool at Dead Horse Point overlooking the Colorado River, Canyonlands National Park, Utah

Tim Fitzharris / Colorado River from Deadhorse Point overlooking Canyonlands National Park, Utah

Tim Fitzharris / Ponderosa Pine (Pinus ponderosa) trees and Mount Herard, Great Sand Dunes National Park, Colorado

Tim Fitzharris / Ponderosa Pine (Pinus ponderosa) trees and Mount Herard, Great Sand Dunes National Park, Colorado

Tim Fitzharris / Mesa, Castle Rock, Castle Valley near Moab, Utah

Tim Fitzharris / Mount Herard, Great Sand Dunes National Park, Sangre de Cristo Range, Colorado

Tim Fitzharris / Mesa, Parriott Mesa, Moab, Utah

Tim Fitzharris / Mesa, Parriott Mesa, Moab, Utah

Tim Fitzharris / Colorado River from Deadhorse Point, Canyonlands National Park, Utah

Tim Fitzharris / Colorado River from Deadhorse Point, Canyonlands National Park, Utah

Tim Fitzharris / Ponderosa Pine (Pinus ponderosa) tree and eroded rock formation, Kasha-Katuwe Tent Rocks National Monument, New Mexico

Tim Fitzharris / Ponderosa Pine (Pinus ponderosa) tree in slot canyon, Kasha-Katuwe Tent Rocks National Monument, New Mexico

Tim Fitzharris / Mountain range reflected in pond, Grand Tetons, Grand Teton National Park, Wyoming

Tim Fitzharris / Mountain range reflected in pond, Grand Tetons, Grand Teton National Park, Wyoming

Tim Fitzharris / Mountain range reflected in pond, Grand Tetons, Grand Teton National Park, Wyoming

Tim Fitzharris / Mountain range reflected in pond, Grand Tetons, Grand Teton National Park, Wyoming

Tim Fitzharris / Sandstone cliffs, Echo Amphitheatre, New Mexico