â¢ equilateral - all 3 sides are equal. 2) By the types of angles they have: â¢ acute triangle - all 3 angles are acute (less than 90Â°) â¢ right triangle - has one right angle (a right angle = 90Â°) â¢ obtuse triangle - has one obtuse angle (an obtuse angle is greater than 90Â° and less than 180Â°).
Over the last 30 years, the time frame for the carving of the Grand Canyon has gone full circle. Thirty years ago, most evolutionists believed the canyon was about 70 million years old. But that estimate changed as radioisotope dating was utilized to show the plateau to be much older than the canyon itself.
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.he younger rocks have already been eroded away by the forces of nature, at least in the immediate vicinity of the Grand Canyon. Some of the younger layers, like the Navajo Sandstone of which the Vermilion Cliffs and the rock of Zion National Park are composed, can be found in the region north of the Grand Canyon.