California and hurricanes, tsunami, and post-disturbance ecosystem changes



by   |  VIEW 232

California and hurricanes, tsunami, and post-disturbance ecosystem changes

Tropical cyclones are produced as a consequence of the sensible heat released by the ocean and then feed thanks to the latent heat of condensation released into the air by the condensing water vapor. They are different from other storms or atmospheric eddies precisely because they have a different energy supply mechanism.

Usually, for tsunamis of seismic origin, the waves have modest amplitude and are not very visible in the open sea, a vessel offshore may not even notice the passage of the tsunami, and concentrate their destructive force near the coast when, due to the shallower bottom, they rise and pour into the hinterland.

The intensity of a tsunami is related to the amount of water displaced at the moment of the formation of the tsunami itself. The study: A multi-proxy record of hurricanes, tsunami, and post-disturbance ecosystem changes from coastal southern Baja California, published on the The Science of the total environment, explained: "Tsunamis and hurricanes are two earth surface processes that can dramatically impact coastal landforms and ecosystems.

This study uses a combination of palynological, grain-size, X-ray fluorescence, and loss-on-ignition analyzes, short-lived isotopic and radiocarbon dating , and statistical analysis to differentiate the tsunami and hurricane deposits, establish a Late-Holocene record of extreme events, and document the landscape and vegetation transformation in response to disturbance events and environmental changes from a small coastal lagoon in Baja California, Mexico.

Prior to ~ 530 cal yr BP, Playa Los Cocos was occupied by a short-hydroperiod tidal marsh bounded by desert vegetation on the surrounding hillslopes. At ~ 530 cal yr BP, a tsunami created a backbarrier lagoon and introduced mangrove propagules from other coastal localities, and the lagoonal environment and substrates also provided suitable habitats for red mangroves to proliferate.

ions rapidly expanded until ~ 180 cal yr BP, when modern human activities diminished the mangrove forest in our study area. Overall, the multi-proxy dataset revealed four hurricane events at ~ 770, ~ 600, ~ 280, and ~ 0 cal yr BP, and one tsunami event at ~ 530 cal yr BP.

The hurricane deposits were preserved in the form of fluvial and slope-wash deposits characterized by low organic and water contents, low concentration of marine elements, and high concentration of terrestrial elements. The tsunami run-up deposits are characterized by abundant broken and intact sea shells, high content of carbonate and marine elements, low concentration of terrestrial elements, and sharp basal contact with the underlying sediments.

The tsunami backwash deposits are characterized by a mixed physical and chemical signature resembling both marine and terrestrial sediments. Results also suggest that both hurricanes and tsunamis can help propagule dispersal and create suitable coastal habitats favorable for the spread and proliferation of mangroves in a desert coastal environment."