(Original headline: You are going to read here about earthquakes, volcanic eruptions, immense...)
You are going to read here about earthquakes, volcanic eruptions, immense underwater volcanoes and landslides, runaway global warming fueled by hidden inventories of gas, and -- yes -- even mega-tsunamis that dwarf the recent calamity in Southeast Asia and eastern Africa.
The most important things to remember: These are not imminent threats. Time scales associated with these events are inconceivably long. You should not be alarmed.
But you should be aware, geologists and other experts say. These natural disasters have happened and will happen again. Dealing with them -- or at least acknowledging them -- is part of the cost of living on a living planet.
''To the average person, things like tsunamis, earthquakes and volcanic eruptions are big deals,'' said Tim Dixon, a professor of geology and geophysics at the University of Miami. ``To geologists, this is like the weather.
``It's not that we don't care -- it's just not a big deal. This is how the Earth works. What is a surprise to us is how surprised people get and generally how unprepared people are.''
One other important note: The awful death tolls associated with recent geologic events do not suggest that the planet is becoming less friendly. They do suggest that more people are living in coastal and other areas subject to severe flooding and in mountainous or other unstable areas subject to earthquakes.
''All of these things appear to be getting worse mostly because there are more and more people living in vulnerable areas,'' Dixon said. ``As usual, humans have made it worse.''
NO ERUPTIONS HERE
Obviously, South Floridians don't need to prepare for a volcanic eruption or an earthquake. The area's geological characteristics -- a flat, sandy, relatively stable foundation -- just don't present those threats.
Our neighbors in the Caribbean, however, must deal with a buffet of geological perils. Some of those -- volcanoes, earthquakes, underwater landslides -- can propel consequences all the way to South Florida, most prominently in the form of tsunamis.
As you will see, these Caribbean-based tsunamis would be relatively benign by the time they reach our shores.
A tsunami is defined as a series of waves produced by a sudden disturbance in sea level, and those that originate in the Caribbean would propel only negligible waves to coastal Florida, experts say.
WHAT IS FEARED MOST
R But some geologists say a ''mega-tsunami'' created by a colossal landslide in the Canary Islands near Africa could surge across the Atlantic Ocean and submerge South Florida and much of the East Coast, the Caribbean and parts of Central and South America under 60 feet of water.
And so, this is where our survey of geological threats will start. Remember, the odds are very low that any of this will happen in your lifetime or that of your children or grandchildren.
• Cumbre Vieja: This is a volcano on the island of La Palma in the Canaries, about 4,000 miles from South Florida. Like most active volcanoes, it grows and collapses in regular, though very lengthy, cycles.
The problem: Cumbre Vieja could be due for another collapse -- an unimaginably huge collapse.
Some scientists, studying ruptures that have appeared on the surface, say a chunk of material larger than the island of Manhattan could break off Cumbre Vieja's western side during an eruption and plunge into the ocean.
A landslide of that magnitude, technically called a ''volcanic flank failure,'' would produce a wide, towering tsunami that could surge across the Atlantic and crash into a vast region stretching from Newfoundland to Brazil. About nine hours after the collapse, a 60-foot-high wall of water could engulf coastal South Florida, these scientists say.
''We haven't studied South Florida precisely, but it could reach several miles inland, maybe all the way to I-95,'' said Steven Ward, a geophysicist at the University of California at Santa Cruz and a leading expert on Cumbre Vieja.
Said Jim Lushine, the National Weather Service's warning coordinator for South Florida, who sometimes must deal with Category 1-5 hurricanes: ``From the ocean-level standpoint, this would be like a Category 10 hurricane.''
How much warning would we have? Well, at least those nine hours. Geologists closely monitor Cumbre Vieja and should be able to issue warnings before an eruption and landslide occur. In addition, a fortified tsunami warning system for the Caribbean and East Coast could be in place by mid-2007.
Still, the area in Miami-Dade and Broward counties requiring evacuation would be larger than current hurricane evacuation zones, and the task of getting everyone out would be monumental.
''You couldn't do it,'' Lushine said. ``We get 24 hours for a hurricane and even that is nearly impossible. Luckily, tsunamis come maybe once every 500 years.''
Actually, this particular event involving Cumbre Vieja occurs even less frequently.
''They happen roughly every 200,000 years,'' Dixon said. ``On the other hand, it's been about 200,000 years since the last one. Yeah, it could happen tomorrow, but it's also about the same likelihood it will happen 10,000 years from now. It's the plus or minus that a lot of people have a problem with.''
Ward, who has published several papers on Cumbre Vieja, agrees.
''It's very unlikely to affect the man in the street,'' Ward said. ``He should be more concerned about getting hit by a car or developing cancer. But other people have other concerns -- governments, corporations, those who deal with rare and catastrophic events should have some concern.''
• Caribbean volcanoes and earthquakes: The outer arc of Caribbean islands sits on or near an active seismic zone. Earthquakes rocked various islands in 1775, 1867, 1918 and 1946, often generating tsunamis. That last one killed about 1,700 people in the Dominican Republic and Haiti.
A study published last year by George Pararas-Carayannis, a marine scientist and former director of the International Tsunami Information Center, found that 88 tsunamis struck the Caribbean region between 1489 and 1998.
''Several of these were generated by volcanic eruptions and by collateral volcanic flank failure, debris avalanches and landslides . . .,'' he wrote in the report published in the Science of Tsunami Hazards, a professional journal. ``The historic record indicates that Caribbean volcanoes pose a serious threat for several islands in the region.''
Among those volcanoes and islands: Mount Pelée on Martinique, La Soufrire on St. Vincent, Soufriere Hills on Montserrat and Kick'em Jenny, an unusual underwater volcano near Grenada.
Some of those recently generated modest tsunamis in the Caribbean, ranging from three to six feet high, though a 2003 tsunami sent a 12-foot wall of water over parts of Montserrat, the study reported.
But it is difficult to envision an event in the Caribbean that would cause a tsunami catastrophe in South Florida, Dixon said.
For one thing, seismic pressures in that area are less intense than those in the Indian Ocean, where December's disaster originated.
For another, South Florida's offshore reef would offer some protection from relatively modest Caribbean-based tsunamis, causing them to break over the reef rather than ashore. That reef is insufficient to shield South Florida from the volume of water that could be generated by Cumbre Vieja, Dixon said.
• Underwater landslides: These do not directly threaten South Florida, but the Caribbean and other areas can be endangered by tsunamis that could follow such events.
In one example of the danger, evidence exists of an underwater landslide off western Norway in which an area the size of Iceland slid into the Norwegian sea about 8,100 years ago. Called the Storegga slide, it produced a tsunami as high as 60 feet in some places. It moved as far as Scotland.
• Gas hydrates: If you must worry, here is something new to worry about.
Scientists say huge reserves of gas hydrates -- ice-like crystalline solids formed by a mixture of water and natural gas, generally methane -- lurk offshore nearly everywhere. Left to their own devices, gas hydrates are harmless. But . . .
''If you warm up the gas hydrate, it breaks down and releases methane,'' Dixon said. ``So if anything ever destabilized those gas hydrate deposits and all of that methane comes out into the atmosphere, we're toast, literally and figuratively.
``It would start to raise the methane concentration of the atmosphere and, in a few years, global warming would really take off.''
What could destabilize the situation? A warmer atmosphere and ocean. In other words, unless we get a handle on global warming soon, a feedback loop could begin that would dramatically accelerate the phenomenon.
NO SCAREMONGERING
But again, those are worst-case scenarios, the time scales are extremely long, and geologists insist that their specialty isn't dedicated merely to scaring the heck out of you.
''There is something good geology can do for you,'' Dixon said. ``We can tell you what to expect and sometimes when to expect it. But people have to listen.''
Do they? Well, for now they do, in the aftermath of the natural catastrophe in Southeast Asia and eastern Africa.
''Nobody listens to geologists, generally,'' Dixon said. ``We have a brief 15 minutes now, but you wait, a year from now . . ..''
