Tsunamis are ocean waves triggered by large earthquakes that occur near or under the ocean, volcanic eruptions, submarine landslides, and by onshore landslides in which large volumes of debris fall into the water.
The term El Niño (Spanish for 'the Christ Child') refers to a warm ocean current that typically appears around Christmas-time and lasts for several months, but may persist into May or June. The warm current influences storm patterns around the globe.
Geology is the study of the Earth. This scientific study includes how the Earth was formed, how the Earth has changed since it was formed, that materials that make up the earth, and understanding the processes that act on it.
The best place for this sort of information is the National Centers for Environmental Information, which is part of the National Oceanic and Atmospheric Administration of the U.S. Department of Commerce.
Coral reefs can be damaged by natural processes, such as storms, but they are increasingly at risk from human activities. Oil spills and pollutants can threaten entire reefs.
No one knows for sure what would happen if the snow and ice in the polar regions all melted. Sea level would rise, which would flood coastal regions. Climate would be affected worldwide.
The USGS has run bathymetric surveys for many marine areas, as well as for rivers and lakes in the US, including Yellowstone Lake, Cra
The USGS has studied sea-surface temperature in many areas around the globe; you can find publications from these studies on the USGS Web site and by searching on the Internet.