Science 8TH

• Sonar sends a sound wave and the sound wave will eventually hit something and bounce off of that object. The reflected sound wave will make its way back to the sonar machine and the sonar machine will calculate distance based on how long it took for the sound wave to return to it. 
• In a sonar map, shallow sections are lighter in color and deep sections are darker in color
• Ocean trenches usually are deep and will likely be dark blue or black. White is the deepest point of the trench
• Longitude is vertically; east and west of the prime meridian. Latitude is horizontally; north and south of the equator.
• To make a scaled timeline you take the number of years and divide it by the number of ticks/lines.
• To find the number of undecayed atoms needed to reach half-life, divide the total number of parent atoms by 2 to get the new number. After each half-life, the number of daughter material increases.
• To find how long a half-life is divide the parent atoms by 2, and look at the x-axis (in a graph) for the number of seconds it takes
• Rocks that are on the bottom of the stratigraphic map are the oldest; rocks that are on the top of the stratigraphic map are the youngest.
• The oldest rock layers, experience sediments, rocks, and materials deposited on top over millions of years. The youngest rock layers are at the top, as they are the farthest away from the oldest rock layers.
• The Mariana Trench formed from a convergent boundary between the Pacific Plate and the Philippine Plate in a subduction zone. The older, denser Pacific Plate subducted beneath the younger, less dense, Philippine Plate. Because the Pacific Plate density is so high, and is the largest tectonic plate, it caused this ocean trench to become the deepest. The crust gets its high density because it faces pressure from the water and sediments above it which compacts the crust. Also as the crust ages it loses heat energy in the molecules, which makes those molecules compact and move slower.
• When the Colorado Plateau was uplifted, possibly because of the mantle flowing upward, and because the North American Plate became thicker, the river eroded the plateau, carving the canyon over time. The river's high elevation and steepness are what primarily caused this to happen. So, after millions of years, with eroding occurring the Grand Canyon formed. 
• The Mariana Trench and Grand Canyon formed similarly because both formations somewhat involved subduction with plate boundaries.