Account for the occurrence of sea level 

• Candidates should define the term “sea-level changes” as a rise or fall in the level of the sea relative to the land or the vertical movement of land relative to the Sea level changes are also referred to as Eustatic changes.
• Candidates should identify and explain the causes of sea – level

Rainfall/precipitation; Increased rainfall/ precipitation (Pluviation) in the upstream areas leads to a rise in sea-level relative to the lands while reduced rainfall, characterized by drought

(dessication) leads to fall in the sea-level relative to the land.

Temperature; reduced temperatures/ low temperatures (such as in winter) causes contraction of water molecules in water bodies leading to a fall in sea-level relative to the land while increase in temperature (say due to vulcanicity) causes expansion of water leading increase in volume.

Glaciation and de-glaciation; De-glaciation which involves ice melting due to increased temperatures leads to a rise in sea-level relative to the land whereas glaciation/formation of ice involves freezing of water on high mountains and polar Regions. This leads

to a fall in sea – level relative to the land.

Sedimentation; Deposition of sediments in ocean basins displaces water upwards, leading to a rise in sea – level relative to the land. E.g. RiverssuchasRufigiandTanadepositalotofalluviumintothesea.Thisdisplaces somewaterandafteranumberofyearsit leads toariseinsealevel

Rivers;  the water deposited (poured) into the sea by rivers such as the Nile in Mediterranean, Tana into the Indian Ocean lead to a rise in the sea level

Reaction of hydrogen and oxygen; it’s believed that hydrogen atoms from the sun often enter the earth’s atmosphere and when they combine with oxygen in the ozone layer, rainfall is formed which enters into the sea to raise its level

Drought; prolonged drought leads to excessive evaporation leading to a fall in the sea level, East Africa for example has been experiencing prolonged drought and reduced rains for the last 50 years. This has led to a fall in the water level of the Indian Ocean and Lake Victoria exposing many features which were once submerged.

Global warming is another cause for rise in sea level. It involves a rise in temperature leading to melting of ice and snow from mountains like the Hi Malaya, Rwenzori, Mt. Kenya and Kilimanjaro. Such water moves down into oceans through rivers.

Human activities like dumping of sewage, garbage, construction of artificial  piers and Hotels on water have all led to a rise in the sea level. Over the world thousands of tones in form of hardcore stones and soils are  deposited in the sea especially near: beaches to construct Hotels. In Uganda Speke Resort hotel at Munyonyo was partly constructed in Lake Victoria through a similar process.

Tectonic movements. These include warping, faulting, vulcanicity etc.

• Warping – up warp of coastal areas and down warp of ocean basins led to fall in sea level while down warping of coastal areas and up warping of ocean basins led to a rise in sea-level/base level,
• Plate-divergence causes expansion of ocean basins leading to a fall in sea level while contraction of ocean basins due to plate convergence leads to a rise in sea-level/base-level.
• Vulcanicity. Volcanism at contractive plate boundaries and subduction zones displaces water upwards, hence a rise in sea-level relative to the
• Isostatic re-adjustments;. Addition of sediments/ loading on continental This causes sinking slowly of continents, hence a rise in sea level. Isostatic uplift of land mass occurs due to ice melting, leading to a fall in sea-level.