ROCKY MOUNTAINS NATIONAL PARK
Front Range north of Boulder, Colorado, USA (looking west from the Great Plains). Rocky Mountains National Park (misnamed “Rocky Mountain National Park” by the American federal government) is part of Colorado's Front Range. The mountains in this area are part of the true Rocky Mountains (not all mts. in western North America are the “Rockies”). The American Rockies are subdivided into three physiographic provinces. This park is part of the Southern Rocky Mountains Physiographic Province, characterized by the common presence of Precambrian-aged igneous and metamorphic rocks.
Long's Peak & Beaver Meadows (looking ~S) in Rocky Mountains National Park, northern Colorado, USA.
The mountains in the background are principally composed of Mesoproterozoic-aged (1.42 b.y.) granites - the Silver Plume Granite (a.k.a. Long's Peak Granite).
The partially forested valley in the foreground is Beaver Meadows, the site of the now-melted Big Thompson Glacier. That was an alpine glacier (valley glacier/mountain glacier) moving downhill (to the left) during the Late Pleistocene (= last Ice Age). The forested ridge behind the greenish meadow is a lateral moraine composed of glacial till.
Silver Plume Granite (a.k.a. Long's Peak Granite) - 1.42 b.y. granite composed of K-feldspar, quartz, biotite mica, and muscovite mica. This is from a roadcut southeast of Rocky Mountains National Park.
Silver Plume Granite (a.k.a. Long's Peak Granite) - 1.42 b.y. granite composed of K-feldspar, quartz, biotite mica, and muscovite mica. These are outcrop photographs from roadcuts along Trail Ridge Road (Rt. 34) in Rocky Mountains National Park.
Left: unweathered Silver Plume Granite - pink speckled granite.
Right: partially weathered Silver Plume Granite. The orangish-colored rock at left is iron-oxide stained granite adjacent to a joint (fracture) that acted as a conduit for groundwater. The whitish-gray speckled granite is bleached granite, again from the influence of water from the joint at left. The pinkish-colored rock at right is unaltered and unweathered Silver Plume Granite.
Xenolith in Silver Plume Granite (Mesoproterozoic, 1.42 b.y.). “Xeno” means “foreign”, while “lith” means “rock”. So, xenoliths are “foreign rocks”. They represent pieces of wall rock that fell into a cooling magma chamber and did not get melted and incorporated into the magma before final solidification.
Ypsilon Mountain in the Mummy Range, northern Rocky Mountains National Park, northern Colorado, USA. The rocks at this mountain are principally late Paleoproterozoic-aged (1.713 b.y.) biotite schists and gneisses.
Hagues Peak Granite at Fairchild Mountain (Mummy Range, northern Rocky Mountains National Park, northern Colorado, USA). The Hagues Peak Granite is early Mesoproterozoic in age (1.48 b.y.).
Iron Dike Gabbro at Hidden Valley (northern Rocky Mountains National Park, northern Colorado, USA). This is a true igneous dike - a planar intrusion that cuts across surrounding country rock. It is composed of Mesoproterozoic-aged (1.316 b.y.) ferrogabbro.
Silver Plume Granite at Rock Cut (Trail Ridge Road/Rt. 34), northern Rocky Mountains National Park, northern Colorado, USA.
The pinkish-grayish rock is pegmatitic granite, a thin injection of Silver Plume Granite (early Mesoproterozoic, 1.42 b.y.). The host rock is the dark, sparkly material at top & bottom - it's late Paleoproterozoic-aged (1.713 b.y.) biotite schist.
Mushroom Rocks - differentially weathered & eroded outcrops of Silver Plume Granite injected into Precambrian metamorphics.
Cream-colored rocks in pedestal of “mushroom” = pegmatitic granite of the Silver Plume Granite (early Mesoproterozoic, 1.42 b.y.).
Dark-colored rocks in cap of “mushroom” - gneisses (late Paleoproterozoic, 1.713 b.y.).
Lava Cliffs to the north of Rt. 34 (Trail Ridge Road), northwestern Rocky Mountains National Park, northern Colorado, USA. The rocks at Lava Cliffs are quite young, compared with the majority of rocks in this park. The rocks at this cliff (see also the close-up outcrop photo below) are Oligocene-aged volcanics. The rock is described in the literature as rhyolitic welded tuff. It's actually a porphyritic obsidian - large crystals set in a black glassy matrix. This material originated as volcanic ash that was deposited and self-lithified ("welded") by the heat of the ash. The heat was sufficient to re-melt most of the material, resulting in black glass.
Geologic Unit & Age: Braddock Peak Volcanic Complex, Upper Oligocene, 27.7 m.y.
Pink snow & snow algae - this remarkably-colored snow is often seen in Rocky Mountains National Park. The coloring agent is biologic. The pink color is from the presence of cryophilic algae. “Cryo” means “ice” or “cold”. “Philic” means “love”. So, ice-loving algae are present. Surprisingly, the algae are not red algae. They're actually green algae (chlorophytes). Dozens of species of snow algae have been described and named in western America. The reddish color is from a carotenoid pigment. The green algae also have chlorophyll, of course.