Lect 5 - Geology

• Hydrologic cycle


  The unending circulation of water among Earth's different spheres - the hydrosphere, the atmosphere, the geosphere, and the biosphere

  
• Earth is the only planet in the solar system that has a global ocean and a hydrologic cycle
• Earth's water reservoirs

  • Oceans
  • Glaciers
  • Rivers
  • Lakes
  • Groundwater
  • Atmosphere
  • Soil moisture

  
• Oceans


  Vast bodies of saltwater that cover a significant portion of Earth's surface
• Seas


  Smaller and partially enclosed by land, with more consistent and higher salinity compared to oceans
• Saline lakes


  Bodies of water with a high concentration of dissolved salts, typically much higher than freshwater lakes but lower than seawater
• Dead Sea


  • Extremely high concentration of dissolved mineral salts in the water causes it to be denser than fresh water, making it easy to float
• Glaciers


  Large, persistent bodies of ice that form over many years as snow accumulates and compresses into dense ice
• Glaciers


  • Found in polar regions, high mountain ranges, and some subpolar regions around the world
• Ice sheets


  Massive expanses of ice that cover large areas of land, primarily in polar regions, distinct from glaciers in that they are not confined to valleys or mountains

  
• Groundwater


  Water located beneath the Earth's surface in soil pore spaces, fractures, rock layers, or other geological formations
• Groundwater


  • A crucial component of the Earth's hydrological cycle, interacting with surface water bodies and the atmosphere
• Atmosphere


  Water in the atmosphere plays a crucial role in Earth's climate system and weather processes
• Rivers


  Natural flowing watercourses that move water from higher elevations to lower elevations, typically draining into a larger body of water
• Rivers

  • Nile River
  • Amazon River
  • Cagayan River
• Swamp


  A type of wetland characterized by saturated muddy, and often partially submerged land, typically found in low-lying areas, along riverbanks, and in coastal regions
• Soil moisture


  The amount of water present in the soil, including both liquid and vapor phases
• Freshwater lake


  A lake that contains water with low salinity or salt content, typically less than 0.5 parts per thousand (ppt), and does not have direct connections to the ocean or sea
• Snow and ice collectively hold a significant portion of the Earth's freshwater reserves
• Evaporation


  The process by which liquid water changes into water vapor (gas), allowing water to enter the atmosphere from the ocean and, to a much lesser extent, from the continents
• Water's paths in the hydrologic cycle

  1. Evaporation

  2. Wind transport of moisture-laden air

  3. Cloud formation and precipitation

  4. Infiltration and groundwater movement

  5. Runoff

  6. Evapotranspiration
• If present-day glaciers were to melt and release all their water, sea level would rise by several dozen meters, submerging many heavily populated coastal areas
• Water balance


  The volume of water that passes through each part of the hydrologic cycle annually, with the amount of water vapor in the air at any one time being just a tiny fraction of Earth's total water supply
• Glaciers


  If present-day glaciers were to melt and release all their water, sea level would rise by several dozen meters. Such a rise would submerge many heavily populated coastal areas.
• The amount of water vapor in the air at any one time is just a tiny fraction of Earth's total water supply.
• Because the total amount of water vapor in the atmosphere remains about the same, the average annual precipitation worldwide must be equal to the quantity of water evaporated.
• Over the oceans, evaporation exceeds precipitation. Because the level of the world ocean is not dropping, the system must be in balance.
• The 36,000 cubic kilometers of water that annually makes its way from the land to the ocean causes enormous erosion. This immense volume of moving water is the single most important agent sculpting Earth's land surface.
• Weathering


  The physical breakdown (disintegration) and chemical alteration (decomposition) of rock at or near Earth's surface
• Erosion


  The removal and transport of weathered rock material by water, wind, or ice
• Sheet flow


  A type of water flow that occurs when water moves evenly over a surface in a thin, continuous layer
• Rills


  Small channels or grooves that form on the surface of soil or loose sediment due to the erosion caused by flowing water
• Gullies


  Larger and deeper channels than rills, characterized by more significant erosion and excavation of the soil or rock substrate
• Streams


  Water that flows in a channel, regardless of size
• Rivers


  A general term for streams that carry substantial amounts of water and have numerous tributaries
• Tributary


  A smaller river or stream that flows into a larger river, lake, or another body of water
• Drainage basin


  The area of land that drains into a stream or river
• Divide


  An imaginary line that separates one drainage basin from another
• River system


  • Includes not only its network of stream channels but its entire drainage basin. It can be divided into three zones
• Dendritic pattern


  The most common drainage pattern, where the branching pattern of streams resembles a deciduous tree