The Grand Canyon is a steep-sided canyon carved by the Colorado River in Arizona, United States. The Grand Canyon is 277 miles long, up to 18 miles wide and attains a depth of over a mile; the canyon and adjacent rim are contained within Grand Canyon National Park, the Kaibab National Forest, Grand Canyon–Parashant National Monument, the Hualapai Indian Reservation, the Havasupai Indian Reservation and the Navajo Nation. President Theodore Roosevelt was a major proponent of preservation of the Grand Canyon area and visited it on numerous occasions to hunt and enjoy the scenery. Nearly two billion years of Earth's geological history have been exposed as the Colorado River and its tributaries cut their channels through layer after layer of rock while the Colorado Plateau was uplifted. While some aspects about the history of incision of the canyon are debated by geologists, several recent studies support the hypothesis that the Colorado River established its course through the area about 5 to 6 million years ago.
Since that time, the Colorado River has driven the down-cutting of the tributaries and retreat of the cliffs deepening and widening the canyon. For thousands of years, the area has been continuously inhabited by Native Americans, who built settlements within the canyon and its many caves; the Pueblo people considered the Grand Canyon a holy site, made pilgrimages to it. The first European known to have viewed the Grand Canyon was García López de Cárdenas from Spain, who arrived in 1540; the Grand Canyon is a river valley in the Colorado Plateau that exposes uplifted Proterozoic and Paleozoic strata, is one of the six distinct physiographic sections of the Colorado Plateau province. Though It is not the deepest canyon in the world, the Grand Canyon is known for its visually overwhelming size and its intricate and colorful landscape. Geologically, it is significant because of the thick sequence of ancient rocks that are well preserved and exposed in the walls of the canyon; these rock layers record much of the early geologic history of the North American continent.
Uplift associated with mountain formation moved these sediments thousands of feet upward and created the Colorado Plateau. The higher elevation has resulted in greater precipitation in the Colorado River drainage area, but not enough to change the Grand Canyon area from being semi-arid; the uplift of the Colorado Plateau is uneven, the Kaibab Plateau that the Grand Canyon bisects is over one thousand feet higher at the North Rim than at the South Rim. All runoff from the North Rim flows toward the Grand Canyon, while much of the runoff on the plateau behind the South Rim flows away from the canyon; the result is deeper and longer tributary washes and canyons on the north side and shorter and steeper side canyons on the south side. Temperatures on the North Rim are lower than those on the South Rim because of the greater elevation. Heavy rains are common on both rims during the summer months. Access to the North Rim via the primary route leading to the canyon is limited during the winter season due to road closures.
The Grand Canyon is part of the Colorado River basin which has developed over the past 70 million years, in part based on apatite /He thermochronometry showing that Grand Canyon reached a depth near to the modern depth by 20 Ma. A recent study examining caves near Grand Canyon places their origins beginning about 17 million years ago. Previous estimates had placed the age of the canyon at 5–6 million years; the study, published in the journal Science in 2008, used uranium-lead dating to analyze calcite deposits found on the walls of nine caves throughout the canyon. There is a substantial amount of controversy because this research suggests such a substantial departure from prior supported scientific consensus. In December 2012, a study published in the journal Science claimed new tests had suggested the Grand Canyon could be as old as 70 million years. However, this study has been criticized by those who support the "young canyon" age of around six million years as " attempt to push the interpretation of their new data to their limits without consideration of the whole range of other geologic data sets."The canyon is the result of erosion which exposes one of the most complete geologic columns on the planet.
The major geologic exposures in the Grand Canyon range in age from the 2-billion-year-old Vishnu Schist at the bottom of the Inner Gorge to the 230-million-year-old Kaibab Limestone on the Rim. There is a gap of about a billion years between the 500-million-year-old stratum and the level below it, which dates to about 1.5 billion years ago. This large unconformity indicates a long period. Many of the formations were deposited in warm shallow seas, near-shore environments, swamps as the seashore advanced and retreated over the edge of a proto-North America. Major exceptions include the Permian Coconino Sandstone, which contains abundant geological evidence of aeolian sand dune deposition. Several parts of the Supai Group were deposited in non–marine environments; the great depth of the Grand Canyon and the height of its strata can be attributed to 5–10 thousand feet of uplift of the Colorado Plateau, starting about 65 million years ago. This uplift has steepened the stream gradient of the Colorado River and its tributaries
The Severn River is a tidal estuary 14 miles long, located in Anne Arundel County in the U. S. state of north of the South River. The Severn has 69 square miles of land. Thus, its total watershed area is 15% water, its source is the beginning of the non-tidal nine-mile long Severn Run in northwestern Anne Arundel County in Severn, Maryland. The river enters the Chesapeake Bay near the major port city of Annapolis the capital of Maryland. Most famous for the United States Naval Academy campus situated at the mouth of the river, the Severn provides an access point to the Chesapeake Bay not just for midshipmen but for fishermen and pleasure boaters. Several tributary creeks drain developed areas, including Weems Creek and its nontidal portion Cowhide Branch, which drain most of the Annapolis Mall and the Anne Arundel Medical Center; the Severn River is crossed by two bridges. One, known as the Severn River Bridge or Pearl Harbor Memorial Bridge, carries US 50/US 301/MD 2 and was first built in 1886.
The other carries MD 450, is now named the "US Naval Academy Bridge" because its south end traverses the academy. The latter bridge was built as a drawbridge in the late 1920s and replaced with the current high span in 1994. A former railroad trestle between the two current bridges, built in about 1887 for the Annapolis and Baltimore Short Line Railroad, was removed post-1968 when it was declared unsafe. On the northshore from Annapolis is the communities of St. Margaret's adjacent to the colonial plantation of Whitehall. If a tributary has sub-tributaries below, they are listed after the "&". North Shore Pointfield Branch Bear Branch Cold Spring Branch Chartwell Branch Stevens Creek & Lake Liberty Rock Cove Forked Creek & Sacketts Pond Yantz Creek & Cedar Creek Sullivan Cove Ringgold Cove Asquith Creek Rays Pond Chase Creek Cool Spring Cove Winchester Pond Manresa Pond Woolchurch Cove & Pond Carr CreekSouth Shore Sewell Spring Branch Indian Creek & Indian Creek Branch Cypress Branch Arden Pond Plum Creek & Gumbottom Branch Valentine Creek Old Place Creek Browns Cove Maynadier Creek & Deep Ditch Branch Hopkins Creek & Davids Run Brewer Pond & Arthurs Run Brewer Creek & Howards Branch Clements Creek & Hockley Branch Saltworks Creek & Cabin Branch Martins Pond Luce Creek & Howard Creek Cove of Cork Weems Creek & Cowhide Branch Shady Lake College Creek & Peters Cove Spa Creek & Acton Cove, Hawkins Cove Lake Ogelton Back Creek Providence, the first colonial settlement in Anne Arundel County, was founded in the fall and winter of 1649–1650 at the beginning of a mass migration of a group of Puritans and non-conformists from Lower Norfolk County in Virginia to the north side of the mouth of the Severn.
It faded away after the 1680s when Annapolis came into favor and, in 1694, became Maryland's capital. This "lost town" of Providence was though to be limited to the Carr Creek and Greenbury Point area across the river from Annapolis on what are now the grounds of Naval Station Annapolis More recent archaeological research has uncovered homes of this scattered settlement further to the north and northeast as well, on the southern half of the Broadneck Peninsula near Whitehall Creek. NOAA Chart of Severn River Severn River history from Anne Arundel County web site A. T. Davison and C. B. Rucker. Gems of the Severn Available from Scenic Rivers Land Trust, http://www.srlt.org Maryland DNR's Surf Your Watershed: Severn River Severn River Association Severn Riverkeeper Severn River Commission College Creek watershed assessment from 2007 Annapolis Forum: Electronic Discussion for Annapolis MD Area Folk The Capital Newspaper Environment section for Severn River and Chesapeake Bay
The Women's road race of the 2015 UCI Road World Championships took place in and around Richmond, United States on September 26, 2015. The course of the race was 129.6 km with the finish in Richmond. Pauline Ferrand-Prévot was the defending champion, having won the world title in 2014. In a sprint finish of a select group of nine riders, Great Britain's Lizzie Armitstead added the rainbow jersey to her UCI Women's Road World Cup overall victory, out-sprinting Dutch rider Anna van der Breggen by just over a wheel's length; the podium was completed by home rider Megan Guarnier, the first American to podium in the event since 1994. Qualification was based on the 2015 UCI Nation Ranking as of August 15, 2015; the first five nations in this classification qualified seven riders to start, the next ten nations qualified six riders to start and the next five nations qualified five riders to start. Other nations and non ranked. Moreover, the outgoing World Champion and continental champions were able to take part in the race on top of the nation numbers.
The women rode eight laps on the road race circuit. The length of the circuit had a total elevation of 103 meters. All road races took place on a challenging and inner-city road circuit; the circuit headed west from Downtown Richmond, working its way onto Monument Avenue, a paver-lined, historic boulevard that's been named one of the "10 Great Streets in America". Cyclists took a 180-degree turn at the Jefferson Davis monument and maneuvered through the Uptown district and Virginia Commonwealth University. Halfway through the circuit, the race headed down into Shockoe Bottom before following the canal and passing Great Shiplock Park, the start of the Virginia Capital Trail. A sharp, off-camber turn at Rockets Landing brought the riders to the narrow, cobbled 200 meters climb up to Libby Hill Park in the historic Church Hill neighborhood. A quick descent, followed by three hard turns led to a 100 meters climb up 23rd Street. Once atop this steep cobbled hill, riders descended into Shockoe Bottom.
This led them to the final 300 meters climb on Governor Street. At the top, the riders had to take a sharp left turn onto the false-flat finishing straight, 680 meters to the finish. All times are in Eastern Daylight Time. 135 cyclists from 46 nations took part in the women's road race. The numbers of cyclists per nation are shown in parentheses. Of the race's 135 entrants, 88 riders completed the full distance of 129.6 km