Lect 6 - Geology

• Shoreline


  The line that marks the contact between land and sea
• Shore


  The land along the edge of a body of water
• Coast


  A larger geographical region that includes the shore as well as the adjacent land areas
• Beach


  An accumulation of sediment found along the landward margin of a water body
• Beaches in the Philippines

  • Boracay (Aklan)
  • Black sand beaches in Albay
  • Sila Island (Northern Samar)
  • Valugan Beach (Batanes)
• White sand


  Due to skeletons or shells of foraminiferas (single-celled marine organisms), corals and other organisms
• Black sand


  Result of eroded volcanic materials such as basalts (dark-colored volcanic rocks)

  
• Pink sand


  Originally white-colored sand beach turned pinkish ever since washed-up red-colored corals spread all over the shore
• Boulder beach


  Huge andesite boulders were produced by Mt. Iraya volcano and these boulders were broken down, polished and rounded by strong waves in Batanes
• Shoreline


  The specific interface or line where land and water meet, dynamic
• Coastline


  A much broader boundary between land and water, has features including rocky cliffs, sandy beaches, or marshy shores, subject to erosion and other natural processes

  
• Wave-cut cliff


  A geological feature formed by the erosion of waves against a coastline

  
• Notch


  A narrow indentation or cutout in the coastline, often formed through erosional processes such as wave action, weathering, or the movement of sediment
• Berm


  A nearly horizontal or gently sloping strip of land or sand found along the backshore of a beach

  
• Foreshore


  The part of the shore exposed at low tide and submerged at high tide, the area where the ocean meets the land

  
• Nearshore


  Extends from the shoreline to where waves break (surf zone) at the outer edge of the surf zone, the area of the ocean where the water is shallow enough to be affected by wave action

  
• Offshore


  The area beyond the nearshore zone, where the water is deeper and further from the shore, associated with activities such as oil drilling, fishing, and shipping
• Sand movement in the beach

  1. Swash (the movement of water rushing up the beach after a wave breaks, carrying sediment and debris landward)

  2. Backwash (the flow of water back down the beach after the swash)

  3. Beach drift (the zigzag pattern of sediment transport along the beach face)

  4. Longshore Current (currents within the surf zone that flow parallel to the shore and move substantially more sediment than beach drift)

  5. Rip Currents (concentrated movements of water that flow opposite the direction of breaking waves)

  
• Shoreline features

  • Erosional features (Wave-cut platforms, Marine terraces, Sea arches, Sea stacks)
  • Depositional features (Spits, Bars, Tombolos, Baymouth bars)

  
• Wave-cut platform


  A gently sloping, flat, or slightly inclined surface of rock that extends from the base of a wave-cut cliff out into the sea

  
• Marine terraces


  Relatively flat or gently sloping landforms that parallel the coastline and are typically found above present-day sea level

  
• Sea arch


  A natural rock arch formed by the erosive action of waves on coastal rock formations
• Sea stack


  A vertical column or pillar of rock that stands isolated from the coastline, often adjacent to cliffs or headlands

  
• Spit


  An elongated ridge of sand that projects from the land into the mouth of an adjacent bay
• Baymouth bar


  A sandbar that completely crosses a bay, sealing it off from the open ocean
• Tombolo


  A ridge of sand that connects an island to the mainland or to another island
• Tropical storms


  Powerful storms characterized by low pressure systems and strong winds, including hurricanes, cyclones, and typhoons
• Storm Surge


  The most devastating damage in the coastal zone, caused by the rise in water level associated with a tropical storm
• Spit


  A ridge of sand that connects an island to the mainland or to another island, forms in much the same manner as a spit
• Bay


  A body of water partially enclosed by land, usually with a wide mouth opening to the sea or another larger body of water, such as a lake or another bay
• Tombolo


  A ridge of sand that connects an island to the mainland or to another island, forms in much the same manner as a spit
• Tropical storms


  • Characterized by low pressure systems and strong winds
• Tropical storms


  • Hurricane (North Atlantic Ocean and Northeastern Pacific Ocean)
  • Cyclone (South Pacific and Indian Ocean)
  • Typhoon (Northwestern Pacific Ocean)
• Storm surge


  A dome of water 65 to 80 kilometers (40 to 50 miles) wide that sweeps across the coast near the point where the eye makes landfall
• The worst surges occur in places like the Gulf of Mexico, where the continental shelf is very shallow and gently sloping. In addition, local features such as bays and rivers can cause the surge to double in height and increase in speed.
• Super typhoon Yolanda made landfall on November 8, 2013 in Guian, Eastern Samar
• Shoreline


  • A dynamic place that can change rapidly in response to natural forces
  • Exceptional storms are capable of eroding beaches and cliffs at rates that greatly exceed the long-term average
  • Such bursts of accelerated erosion not only significantly affect the natural evolution of a coast but also can have a profound impact on people who reside in the coastal zone
• Hard stabilization

  • Jetties
  • Groins
  • Breakwaters
  • Seawalls
• Jetties


  Structures typically built from a shoreline out into a body of water, often the sea or a river, to direct currents and prevent sediment deposition. They're also used for docking boats or ships.
• Jetties act as a dam against which the longshore current and beach drift deposit sand


  At the same time, wave activity removes sand on the other side