Podcast
Questions and Answers
What is the dominant mechanism in both erosion and deposition along coastlines?
What is the dominant mechanism in both erosion and deposition along coastlines?
Wave action
What are the main sources of beach sediment?
What are the main sources of beach sediment?
Eroding cliffs of soft Pleistocene material and river delta deposition
What causes disturbance of the longshore drift budget?
What causes disturbance of the longshore drift budget?
Coastal engineering works
How are beaches formed?
How are beaches formed?
Signup and view all the answers
What prompts renewed erosion or deposition on any shoreline?
What prompts renewed erosion or deposition on any shoreline?
Signup and view all the answers
What causes beach starvation down-drift and renewed erosion?
What causes beach starvation down-drift and renewed erosion?
Signup and view all the answers
What is the main cause of beach starvation?
What is the main cause of beach starvation?
Signup and view all the answers
What are tsunamis and how are they formed?
What are tsunamis and how are they formed?
Signup and view all the answers
What is the recommended defense against tsunamis?
What is the recommended defense against tsunamis?
Signup and view all the answers
What are some examples of efficient sea defenses?
What are some examples of efficient sea defenses?
Signup and view all the answers
How long does it take for tsunamis to travel from the earthquake source to distant shores?
How long does it take for tsunamis to travel from the earthquake source to distant shores?
Signup and view all the answers
What are some examples of beach control measures?
What are some examples of beach control measures?
Signup and view all the answers
What are sabkha sediments and where are they formed?
What are sabkha sediments and where are they formed?
Signup and view all the answers
What is the main cause of coastal ground conditions for structures?
What is the main cause of coastal ground conditions for structures?
Signup and view all the answers
What are some examples of economical alternatives for sea walls?
What are some examples of economical alternatives for sea walls?
Signup and view all the answers
What is the main source of modern sea level rise?
What is the main source of modern sea level rise?
Signup and view all the answers
Wave action is the dominant mechanism in both erosion and deposition along coastlines. Waves are powerful due to their pounding action but are also very selective in etching out rock weaknesses and controlling sediment deposition. The largest and most powerful waves are those which have travelled furthest, i.e. have the greatest ______.
Wave action is the dominant mechanism in both erosion and deposition along coastlines. Waves are powerful due to their pounding action but are also very selective in etching out rock weaknesses and controlling sediment deposition. The largest and most powerful waves are those which have travelled furthest, i.e. have the greatest ______.
Signup and view all the answers
Main sources of beach sediment are eroding cliffs of soft Pleistocene material, and also river delta ______.
Main sources of beach sediment are eroding cliffs of soft Pleistocene material, and also river delta ______.
Signup and view all the answers
On any shoreline, erosion and the production, transport and deposition of sediments are all finely balanced; any disturbance of the budget prompts renewed erosion or deposition to recover the ______.
On any shoreline, erosion and the production, transport and deposition of sediments are all finely balanced; any disturbance of the budget prompts renewed erosion or deposition to recover the ______.
Signup and view all the answers
Longshore drift is due to oblique upwash of impacting waves, then backwash directly down beach slope – always away from waves arriving with greatest ______.
Longshore drift is due to oblique upwash of impacting waves, then backwash directly down beach slope – always away from waves arriving with greatest ______.
Signup and view all the answers
Beaches are formed by sand deposition where wave upwash (swash) is greater than the backwash due to water soaking down into the porous ______.
Beaches are formed by sand deposition where wave upwash (swash) is greater than the backwash due to water soaking down into the porous ______.
Signup and view all the answers
Longshore drift budget is easily disturbed by coastal engineering works, most notably where sediment is trapped or deflected into deeper water, so that beach starvation down-drift causes renewed ______.
Longshore drift budget is easily disturbed by coastal engineering works, most notably where sediment is trapped or deflected into deeper water, so that beach starvation down-drift causes renewed ______.
Signup and view all the answers
Deposition occurs in the lee of any obstacle, where sand is drifted into deep or slack water; Carbonate sediments in shallow water create varied and difficult ground conditions for coastal and off-shore structures. Sabkha sediments include gypsum and carbonate, both weakened by karstic solution cavities, interbedded with muds; formed in lagoons along arid coastlines.
Deposition occurs in the lee of any obstacle, where sand is drifted into deep or slack water; Carbonate sediments in shallow water create varied and difficult ground conditions for coastal and off-shore structures. Sabkha sediments include gypsum and carbonate, both weakened by karstic solution cavities, interbedded with muds; formed in lagoons along arid coastlines.
Signup and view all the answers
Efficient sea defence is porous to absorb wave energy; made of armour stone (blocks of >2 tonnes), concrete tetrapods, or massive wall faced with cellular concrete. Reflected waves off solid face may induce scour. Sea walls may cost £5M/km. Economical alternative on long eroding coast (e.g. Holderness) is to create hard points – short sections of stable, fully defended shore – with intervening coast left unprotected.
Efficient sea defence is porous to absorb wave energy; made of armour stone (blocks of >2 tonnes), concrete tetrapods, or massive wall faced with cellular concrete. Reflected waves off solid face may induce scour. Sea walls may cost £5M/km. Economical alternative on long eroding coast (e.g. Holderness) is to create hard points – short sections of stable, fully defended shore – with intervening coast left unprotected.
Signup and view all the answers
Groynes are timber, concrete or steel barriers across beach, which prevent or reduce longshore ______ by trapping sediment.
Groynes are timber, concrete or steel barriers across beach, which prevent or reduce longshore ______ by trapping sediment.
Signup and view all the answers
Tsunamis are large waves generated by seabed earthquake movements; they form in series of 1– 6 waves. In the open ocean they are long and low, but their fronts slow down in shallow water, and can build up to >10 m high approaching a shoreline; they reach maximum ______ in tapering inlets. Best defence is warning and coastal evacuation.
Tsunamis are large waves generated by seabed earthquake movements; they form in series of 1– 6 waves. In the open ocean they are long and low, but their fronts slow down in shallow water, and can build up to >10 m high approaching a shoreline; they reach maximum ______ in tapering inlets. Best defence is warning and coastal evacuation.
Signup and view all the answers
Sediment input and output, by longshore drift, must be in balance to maintain a stable beach. Many artificial ______ – trapping drift on a groyned beach, reducing erosion with a sea wall, deflecting sediment at a harbour mouth – reduce onward drift, and therefore cause beach starvation at down-drift sites.
Sediment input and output, by longshore drift, must be in balance to maintain a stable beach. Many artificial ______ – trapping drift on a groyned beach, reducing erosion with a sea wall, deflecting sediment at a harbour mouth – reduce onward drift, and therefore cause beach starvation at down-drift sites.
Signup and view all the answers
Pleistocene sea levels fell by about 150 m when water was trapped in continental ice sheets, and some land areas were depressed as much as 50 m by ice weight. Raised beaches have abandoned cliffs, dry sea caves and fossil beach sediments. Modern sea level ______ is about 2 mm per year worldwide, due to thermal expansion of seawater (and also to glacier melting); this rate may double with any increased rate of global warming (whether caused by nature or by man’s activities).
Pleistocene sea levels fell by about 150 m when water was trapped in continental ice sheets, and some land areas were depressed as much as 50 m by ice weight. Raised beaches have abandoned cliffs, dry sea caves and fossil beach sediments. Modern sea level ______ is about 2 mm per year worldwide, due to thermal expansion of seawater (and also to glacier melting); this rate may double with any increased rate of global warming (whether caused by nature or by man’s activities).
Signup and view all the answers
Rainfall (precipitation) is the ultimate source of all fresh water, and when it l.
Rainfall (precipitation) is the ultimate source of all fresh water, and when it l.
Signup and view all the answers
Deposition occurs in the lee of any obstacle, where sand is drifted into deep or slack water; Carbonate ______ in shallow water create varied and difficult ground conditions for coastal and off-shore structures. Sabkha ______ include gypsum and carbonate, both weakened by karstic solution cavities, interbedded with muds; formed in lagoons along arid coastlines.
Deposition occurs in the lee of any obstacle, where sand is drifted into deep or slack water; Carbonate ______ in shallow water create varied and difficult ground conditions for coastal and off-shore structures. Sabkha ______ include gypsum and carbonate, both weakened by karstic solution cavities, interbedded with muds; formed in lagoons along arid coastlines.
Signup and view all the answers
Sea walls may cost £5M/km. Economical alternative on long eroding coast (e.g. Holderness) is to create hard points – short sections of stable, fully defended ______ – with intervening coast left unprotected. concrete tetrapods
Sea walls may cost £5M/km. Economical alternative on long eroding coast (e.g. Holderness) is to create hard points – short sections of stable, fully defended ______ – with intervening coast left unprotected. concrete tetrapods
Signup and view all the answers
Many artificial measures – trapping ______ on a groyned beach, reducing erosion with a sea wall, deflecting sediment at a harbour mouth – reduce onward , and therefore cause beach starvation at down- sites.
Many artificial measures – trapping ______ on a groyned beach, reducing erosion with a sea wall, deflecting sediment at a harbour mouth – reduce onward , and therefore cause beach starvation at down- sites.
Signup and view all the answers
