18B. Describe two different processes (connected to different mechanisms) that cause down- and upwelling.
Upwelling and Downwelling refers to the upwards and downwards movment of water molecules in the ocean system. Downwelling happens when near-surface water sinks and upwelling is the subsurface waters rising. Downwelling occurs when the water at the surface of the ocean becomes denser than the water below it, this dense water then sinks. Water becomes dense when it becomes saltier or colder as a result of freezing or moving to colder regions. It may also be caused by the winds, if the wind blows surface water towards the coast this can cause an oversupply of water along the shore which must sink. On the other hand, if these winds blow surface water offshore this creates a deficit of water near the coast and …show more content…
Please describe at least three different ways to preserve beaches and what effects these methods might have.
Groins, concrete or stone wall’s: These can be built out perpendicular to the shore and are used to prevent beach drift from removing sand. A side effect of this method can be the accumulation of sand on the upside of the walls which forms a long triangular wedge. On the downdrift side however sand erodes away.
A breakwater may be developed, an offshore wall that sits parallel or at an angle to the beach. This prevents the full force of the waves hitting the beach and absorbs the majority of energy that, had the wall not been there hit the beach full on. Over time however, sand builds up of the lee side of the breakwater and the beach can grow seawards.
To stop erosion the construction of a sea wall out of large stone or reinforced concrete. These blocks are placed on the landward side of the backshore zone and are designed to reflect wave energy back to sea. These sea walls however, actually increases the rate of erosion at the foot of the sea wall. The result of this may cause the sea wall to be undermined during a large
Upwelling and Downwelling refers to the upwards and downwards movment of water molecules in the ocean system. Downwelling happens when near-surface water sinks and upwelling is the subsurface waters rising. Downwelling occurs when the water at the surface of the ocean becomes denser than the water below it, this dense water then sinks. Water becomes dense when it becomes saltier or colder as a result of freezing or moving to colder regions. It may also be caused by the winds, if the wind blows surface water towards the coast this can cause an oversupply of water along the shore which must sink. On the other hand, if these winds blow surface water offshore this creates a deficit of water near the coast and …show more content…
Please describe at least three different ways to preserve beaches and what effects these methods might have.
Groins, concrete or stone wall’s: These can be built out perpendicular to the shore and are used to prevent beach drift from removing sand. A side effect of this method can be the accumulation of sand on the upside of the walls which forms a long triangular wedge. On the downdrift side however sand erodes away.
A breakwater may be developed, an offshore wall that sits parallel or at an angle to the beach. This prevents the full force of the waves hitting the beach and absorbs the majority of energy that, had the wall not been there hit the beach full on. Over time however, sand builds up of the lee side of the breakwater and the beach can grow seawards.
To stop erosion the construction of a sea wall out of large stone or reinforced concrete. These blocks are placed on the landward side of the backshore zone and are designed to reflect wave energy back to sea. These sea walls however, actually increases the rate of erosion at the foot of the sea wall. The result of this may cause the sea wall to be undermined during a large