Physical Geography

• open system = transfers both energy and matter across its boundary e.g a section of coastline
• closed system = transfers energy but not matter e.g Water cycle
• positive feedback = change in inputs brings about greater amplified change e.g global warming -> more ice melts -> more C02 in atmosphere
• negative feedback = a change in inputs is balanced out, change is nullified e.g more CO2 -> increases photosynthesis -> less CO2
• cascading system = when one system is a component of another = its outputs are another inputs
• isolated system = has no interactions beyond its boundary - very rare e.g in a lab or the earths core
• earths 4 sub-systems = Atmosphere, Cyrosphere, Lithosphere and Biosphere
• Tides = the gravitational attraction between the earth and the moon causes the oceans to bulge out towards the moon
• Neap Tide = small tidal range, sun and moon are perpendicular, quarter moon less gravitational pull - smaller bulge. smaller foreshore so more erosion.
• Spring tide = large tidal range, sun and moon are parallel, full/new moon greater gravitational pull - larger bulges. bigger backshore so more deposition.
• Ocean Currents - influenced by temperature and salinity of ocean. They redistribute heat and transport sediment. Circular pattern , clockwise in North, warm currents move away from equator, cold move towards e.g Gulf Stream - North America to the Atlantic
• Rip Currents = local scale currents. drag sediment off shore. formed when plunging waves cause a temporary build up of water or where off shore sand bars funnel water
• Wind + Waves = waves are caused by the wind dragging water on the surface , called the fetch . e.g UK's fetch is from the South West
• Wave formation = circular orbit turns into elliptical orbit , wave length and velocity decrease , water breaks as the swash
• Destructive waves = plunging, strong backwash , frequency of 13-15 per minute, happen during local storms
• Constructive waves = low and flat , frequency of 8 per minute , strong wash
• Factors affecting wave energy: Wind, fetch, water depth , off shore sediment , topography , tectonic movements, gradient of beach sediment, shape of coastline
• High energy coastline = erosion exceeds deposition , long fetch in direction of prevailing wind e.g Lannacombe bay
• Low energy coastline = deposition exceeds erosion , few currents , wave refraction , off shore sediment e.g Borth Beach
• Wave refraction = as waves hit a headland their energy is concentrated around the headland but reduced in the bays
• Sediment cells = a stretch of coastline bordered by headlands where the movement of sediment is contained. Inputs - cliffs , rivers , LSD, off shore, glaciers. Flows - LSD, currents , traction , saltation Stores - beach , off shore bank , spit, sand dunes
• Sediment budget = balance between changes in the volume of sediment held in the system and the volume of sediment entering/leaving the system. Positive - more inputs than outputs, Negative - more outputs than inputs
• Weathering = the breakdown of rock in situ - sub aerial = land based processes
• Corrosion = erosion of rocks as chemicals in the water get into the rocks e.g carbonic acid dissolves limestone
• Corrasion = chipping of rocks
• Abrasion = smoothing of rocks
• Hydraulic Action = sheer force of waves causing air to go into rocks
• Cavitation = air bubbles in the cliff face expand and break rock
• Wave quarrying = force of up to 11,000 kg/m3 of waves hitting the cliff causing large pieces of rock to break off
• Attrition = particles colliding
• Salt Crystal Growth = salt crystals expanding the rock from the sea, forcing cracks in the rock apart
• Carbonation = atmospheric CO2 dissolves to form carbonic acid that dissolves rocks like limestone
• Chelation =  organisms produce organic substances, known as chelates, that have the ability to decompose minerals and rocks by the removal of metallic cations.
• Oxidation = rock minerals lose ions in oxygen , rock becomes brittle
• Frost wedging = water in rock freezes and expands forcing cracks in rock apart
• Mass movement = downslope movement of regolith when sheer stress exceeds sheer strength
• Sheer strength is reduced when cohesion between particles decreases e.g pores get saturated
• Causes of mass movement = removal of vegetation, weathering , increase gradient, heavy rainfall , earthquakes
• Factors affecting marine erosion = beaches , fetch , weathering , wave refraction, underwater topography , geology , wind speed
• soil creep = occurs on slopes under 5 degrees , moves 1-2 cm per year. when repeated expansion and contraction occurs in the sediment ( freeze thaw)