And It's Getting Deeper. At the Grand Canyons deepest point, it is over a mile (1.83 kilometers) from its top to its floor. A landform is a feature on the Earth's surface that is part of the terrain. Mountains, hills, plateaus, and plains are the four major types of landforms. Minor landforms include buttes, canyons, valleys, and basins. Tectonic plate movement under the Earth can create landforms by pushing up mountains and hills.
The cell cycle. Actively dividing eukaryote cells pass through a series of stages known collectively as the cell cycle: two gap phases (G1 and G2); an S (for synthesis) phase, in which the genetic material is duplicated; and an M phase, in which mitosis partitions the genetic material and the cell divides. 1  G1 phase. Metabolic changes prepare the cell for division. 2  At a certain point-the restriction point-the cell is committed to division and moves into the S phase. 3  S phase. 4  DNA synthesis replicates the genetic material.
Some 90 percent of a cell's time in the normal cellular cycle may be spent in interphase. 1  G1 phase: The period prior to the synthesis of DNA. 2  S phase: The period during which DNA is synthesized. 3  G2 phase: The period after DNA synthesis has occurred but prior to the start of prophase. The cell synthesizes proteins and continues to increase in size. Note that the G in G2 represents gap and the 2 represents second, so the G2 phase is the second gap phase.