. The continent we live on. Physical geography; Natural history. west side you may look into the Grand Canyon of Saint Helena, from which the river debouches onto a narrow sand-covered plain supporting a forest of huge willows and cottonwoods. Both natural and some artificial meadows of lush grass border this on the north side. The south bank lies at the foot of a gigantic cliff. That is Mexico. Most of the Big Bend area is extremely arid, the valleys and the slopes being covered with cactus scrub and some of the taller mountains being completely bald. The rocks sometimes take grotesque shapes
. The continent we live on. Physical geography; Natural history. west side you may look into the Grand Canyon of Saint Helena, from which the river debouches onto a narrow sand-covered plain supporting a forest of huge willows and cottonwoods. Both natural and some artificial meadows of lush grass border this on the north side. The south bank lies at the foot of a gigantic cliff. That is Mexico. Most of the Big Bend area is extremely arid, the valleys and the slopes being covered with cactus scrub and some of the taller mountains being completely bald. The rocks sometimes take grotesque shapes, and large arroyos have been carved out of the uncompacted surface strata and the outwash soils. Despite their towering heights, the Chisos and associated mountains are formed of an ancient plateau that "fell" or sank some thousands of feet into the earth between two faults. Later, the middle of this block was upfolded by pressures from beneath; then vol- canicity added its efforts, further elevating the surface and pour- ing out massive strata of lava. Thus, today, the Chisos rise from a hole in a plateau, but to a height that carries their peaks well above its general level. The Cacomistle or Ring-tailed Cat, a small, soft-furred, and agile type of raccoon found all over the West and Southwest. It can squeeze into tiny The rocks of the old plateau were formed under a sea that very long ago extended up the center of this continent from the Gulf of Mexico to the Arctic Ocean and that later formed great lagoons, coastal swamps, and lakes. Coal beds were laid down in these and the fossil remains of dinosaurs are now to be found in them. Above these are later strata of the Tertiary period, the age of mammals, which contain certain long-extinct animals of great interest, known as Hyracotheres. These were nondescript mam- mals, the size of a large dog, with five toes in front and four behind, all of which terminated in tiny hoofs. They were members of the stock
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