December solstice marks shortest day north of equator and longest day south. Sun reaches Tropic of Capricorn, marking southernmost latitude during year. Earth's axis tilts 23.4° relative to ecliptic plane
May is the fifth month in the Gregorian calendar with 31 days. Named after Maia, goddess of growth, and birth flower is lily of the valley. Marks astronomical spring in Northern Hemisphere and fall in Southern Hemisphere
March is the third month in the Gregorian calendar with 31 days. Named after Mars, the Roman god of war. Marks the beginning of spring in northern hemisphere
Weathering is the deterioration of rocks through water, gases, sunlight and organisms. Physical weathering breaks rocks without chemical change using heat, water and wind. Chemical weathering involves reactions with water, gases and biological organisms. Water is the principal agent in both types of weathering
Sunbeam is a parallel beam of sunlight appearing from the Sun's position. Particle-scattered sunlight appears as parallel shafts separated by shadows. Scattering particles can be air molecules or particulates
Scree is broken rock fragments at cliff bases formed through periodic rockfall. Term comes from Old Norse "skriða" meaning landslide. Loosely synonymous with talus, which accumulates at rock slopes