A blood transfusion is a safe, common procedure in which blood is given to you through an intravenous (IV) line in one of your blood vessels. Blood transfusions are done to replace blood lost during surgery or due to a serious injury. A transfusion also may be done if your body can't make blood properly because of an illness. During a blood transfusion, a small needle is used to insert an IV line into one of your blood vessels. Through this line, you receive healthy blood. The procedure usually takes 1 to 4 hours, depending on how much blood you need. Blood transfusions are very common.
1 The roots of the ancient mountain range that now lies at the bottom of the Grand Canyon were formed about 1.7 billion years ago. 2  There is then an unconformity of about 450 million year in which the rocks are missing. 3  At 1.25 billion years ago the first sedimentary layer, the Bass Formation, was laid down.
The Grand Canyon is one of the worldâs most awesome erosional features. It is 277 miles (446 km) long, including the 60 miles (96 km) of Marble Canyon upstream.The depth of the main segment of the Grand Canyon varies between 3,000 and 6,000 feet (900 and 1,800 m), with the rim-to-rim width between 4 and 18 miles (6 and 29 km).Its origin has plagued geologists since the time of John Wesley Powellâs first courageous voyage down the Colorado River in 1869.n example of how quickly water can erode through the formations of the Grand Canyon region took place on June 28, 1983, when the pending overflow of Lake Powell required the use of the Glen Canyon Damâs 40-foot (12-m) diameter spillway tunnels for the first time.