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New Book Explores Forces That Shaped California's Coast

California's San Andreas Fault seen in this undated photo by USGS.
USGS
California's San Andreas Fault seen in this undated photo by USGS.
How Waves, Earthquakes And Other Forces Shaped San Diego's Coastline
How Waves, Earthquakes and Other Forces Shape San Diego's Coastline GUEST:Keith Heyer Meldahl, author, "Surf, Sand, And Stone: How Waves, Earthquakes, and Other Forces Shape the Southern California Coast"

This is KPBS midday edition. And Maureen Cavanaugh. It does not take a mega-earthquake to reshape the geography of Southern California. It takes thousands of tiny quakes that happen every day. It takes the constant pounding of the waves and it takes a deep underground pressures that are constantly moving and changing the earth. Learning about the elements that have shaped our environment is as close to how the landscape is changing now and how might be vulnerable to extended drought or through strong El Niño. Joining me is can Meldahl professor of geology at Mira Costa college. His near book about our ever-changing landscape is called "Surf, Sand and Stone: How Waves, Earthquates and Other Forces Shape the Southern California Coast". This call will come to the program. Thank you for having me. We have a tendency to think our land and coastal environment is unchanged. Like La Jolla Cove always be there. The beaches the mountains and they have all been formed the much for good. Some geological changes are taking place all the time our tape. They are and some are not all that settle. If you want to go back the last few centuries are bluffs have eroded by 100 feet. For example if you wish to stand at the top of the bluffs that could La Jolla and go back to 100 years when Columbus was crossing you would have to walk another feet hundred feet to get to the edge. The retreat on average of 3 inches per year. The bluffs can stay stable for 30 years and think it is never going to change and then boom 10 feet it hits the beach overnight. If you want to spin the clock back to even longer periods of time, our whole area has undergone a radical makeover geographically speaking as these two tectonic plates it sandwiched in each of gun the several ways. Is that the major element in what is changing our environment? The rubbing together of these tectonic plates? That is the fundamental thing. The rubbing together of the plates has basically shattered the Earth's crust into dozens of big faults. I think people think the San Andreas is the big one. That's the one they make a movie about. But there are many more much closer to San Diego. The other factor is the changing levels of the sea. During the ice ages the seas go up and see goes down. We have the illusion because it happens to have been stable for a millennia that the cc of the place. But for most of geological time the seas have been dropping a rising significantly over centuries. I love the way you say only 500 years ago. Yes it is H and I suppose. It does what you're talking about geologic time. I think when we fool ourselves into thinking their stability we are asking for trouble. When people settled in Southern California after World War II they pushed their houses and businesses up to the edge of the CZK the edge of the stable feature. But it is not. It is there because the sea after the last Ice Age rose to its present level and has been tapping away at the land and pushing the land back by a large amount. We throw our businesses and homes right up to that edge and then dump a bunch of cement on the beach to try to stop the process. We are only postponing the inevitable. You talked about the San Andreas fault and we think that's the only major fault in California. Of course that's quite wrong. But it is the one we hear the most about. Is the one that has the most activity on it? Yes. Certainly the one we should hear most about. Because all the fault here is the longest one. The forward is capable of producing the largest earthquake. And the southernmost section of the fault By which I mean the section that has Northwest towards the end reading it. That is the worrisome section of the file because they have not had a major earthquake for more than 300 years. Whereas other sections of the San Andreas have had big quake since the 1857 quake. Those have relieved a lot of the accumulating strain of the fault. There is the southernmost section senior building straight. It's been constraint because we can measure the rocks bending on either side of the fault for many miles in both directions accepting a rubber band. He can only do that so far before it snaps. That San Diego is not the main target of that kind of a rupture is it? What it had other places to the north and to the east of us more strongly? Yes. It would probably hit Los Angeles for a badly and also all the way over to Santa Barbara. This areas would be that much worse because they are closer to the fault. Also Los Angeles is the worst place in the world to build a big city for think about earthquakes because the basin is filled in with thousands of feet of sand and gravel that has eroded off the mountains. That shakes a lot worse when you have an earthquake. Were San Diego spoke mostly on bedrock. Since we're talking about geological time and 500 years is just yesterday, a lot of people joke about this area west of the San Andreas Fault eventually sort of cracking off the mainland. And disassembled for the mainland. Is that a possibility? Yes. I think it is. What's not a possibility is that it will crack away and sink into the sea which is a major plot of Superman back in 1970 with Christopher Reeves movie. And Lex Luther was going to detonate a missile along the fault and all that beachfront property would fall into the desert. But what you could do is separate and become a long skinny island off the coast of California. In my book I have some tangible scenarios. Realistic although imaginary about how the geography would change. Big ocean basins might open up the bottom for example. Or Baja plus San Diego plus Los Angeles will become a long skinny island heading toward San Francisco. Those are all well with an expectation. And speaking with Keith Meldahl in his new book is called "Surf, Sand and Stone: How Waves, Earthquates and Other Forces Shape the Southern California Coast" . You mentioned Keith the idea that even the water level, the sea level, has not been constant. What does history tells about the rising sea level and what might do to our cause? That long period of stability and mentioned that happened essentially after the last ice age and in the sea rose roughly 400 feet questions present level by about 6000 years ago. That long. Stability seems to be coming to an end. In the last century we have had the secret about 7 inches which is not Celica great deal but projections are accelerating. We think we can have anywhere from 2 feet to 6 feet arise by 2100. Is that a lot or a little? The tide rises and falls by 6 feet here in San Diego see might think so what. But in fact the fee rises 6 feet that means like tide is going to be were high tide us today at high tide is going to be breaking against the block with the beach. And compounding that is the problem that our beaches, which represents the best buffer against the erosion by the waves, the beaches are thinking. Beaches are dynamic systems. The sand comes and goes. If you don't have the sand coming in at the same rate it is leading them to be to shrink. Then we have a problem with drinking beaches and rising seas that leads us into -- and people really already there it's just going to get worse -- it really chronic coastal erosion progress -- problem. Now with El Niño bringing more rain than usual we've already seen a major mudslide in Los Angeles. But other areas of honorable? Any place that has a steep slope could go any mudslide. Especially a place that is burned recently. The recent drought does not help either because the plants are not as strong and healthy in terms of the plants and the roots holding the syrup together. Certainly the amount of the erosion and is going to be significant. After the 1978 with El Niño taking my students to the beach we were walking across rocks and having the Wade Internet will tighten pools because there is no beach left. It is unfortunate because we had a cute replenishment in North County back in 2012. To the tune of $28 million that prompt a vast amount of sand onto the beach. We will see how much of it is here a year from now. Is that like a hopeless task doing that? I don't think it's hopeless because I don't agree have a choice. Ultimately you have to decide if you're going to even have a beach. There are economics and quality-of-life reasons to keep the beach. But there's no question that nature has a way of taking your sand away. Even in a non-El Niño year the sand is drained away because it gets pushed south by the ways and ends up draining into simmering tensions. That continuous loss of sand is normally balanced by an influx of sand from rivers and from the natural retreat of the coastline. The bluffs, as they rode add new sand to the beach. We put up see what seawalls and it's like you have a bank account we stop putting deposited be still have withdrawals in your bank account and it's freaking. The sand bank accounts of Southern California are shrinking. That brings me to a larger question. We like the idea of preserving things the way they are. You mentioned trying to preserve the beaches, putting outbreaks so we don't get as much erosion. But the coast remains the way it is. Our environment remains the way it is. Is trying to do that hurtful to the environment? Or is there really any way to slow down these natural processes? If the sea was not rising and we did not have a warming world to which all realistic projections .2. If it was that he would hold the line for a long time at great expense primarily in the form of seawalls and sustained beach replenishment to make up for the natural losses of the sand. But I think we're facing a problem where with the sea rising if we're going to embrace beach replenishment we're going to have to pump and of sand on the beach as to not only keep up with natural losses of sand but keep up with the rising sea. In terms of harm to the environment yes. There's always an environmental tradable we do major work. In this case the dredged sand that comes to our beaches primarily comes from offshore and fairly shallow waters. You pump the sand out of that and anything living there is not going to survive. On the other hand there are vast areas in between those dredged sites, the burrow pits as they call them which are undisturbed. That is where your nearshore environment will be sustained. I was wondering as your speaking, you're talking about we can see the way that our environment and our landscape is changing by see the erosion of the beaches and the bluffs receding and so forth. Is there any other thing people can look at and say, you know, that is changing. I can see is going down going higher. Whereabouts can people go in San Diego to sort of see the changing landscape? In the appendix of my book I have a series of field trip recommendations. The top of Mount so that you can still kind of stuff there. You can still roads Canyon fault that is pushed up the mountain. You can see the old marine terraces like flights of stairs to climb from the beach inland. Each one created by former sea level. When you see that and realize the sea used to be breaking there, it's not because the sea was higher than it is today its cousin levels lower. Every Tennessee was topping with the land the land has been pushed out. So the old shorelines away above the sea. What you cannot see it happening today, you can see the result left of millions of years. It is a dramatic change in the landscape. You have any suggestions in the book how people can adapt to the changes? There are a couple of lessons we can think about when you understand the geologic and oceanographic here. Earthquakes and tsunamis have happened here a lot of times and it will happen here again. We cannot predict when we can surly be prepared. I would recommend everyone be prepared to survive for three days with enough food and water and without electricity or gas. So food and water in a big first aid kit or camping stuff to make your plan to meals less unpleasant and to help you unprepared neighbors. Basically the sea and the earth are going to do they want to do? Yes. We can hold them off for a while. But I don't think we can stop them. I have been sticking with Keith Meldahl. His book is called "Surf, Sand and Stone: How Waves, Earthquates and Other Forces Shape the Southern California Coast". Thank you so much. Thank you it's been my pleasure.

Cover of book, "Surf, Sand, and Stone: How Waves, Earthquakes and Other Forces Shape the Southern California Coast" by Keith Heyer Meldahl.
Cover of book, "Surf, Sand, and Stone: How Waves, Earthquakes and Other Forces Shape the Southern California Coast" by Keith Heyer Meldahl.

Learning about the elements that have shaped geologic environment in Southern California gives people clues to how the landscape is changing now and how it may be vulnerable to an extended drought or strong drought or strong El Niño.

A new book by a Mira Costa College geology professor shows it doesn't take a mega-quake to reshape the geography. Research shows thousands of tiny quakes occur daily,and they provide the deep underground pressures that are constantly moving and changing the earth.

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This is just one of the points made by Keith Heyer Meldahl in his book, "Surf, Sand, and Stone: How Waves, Earthquakes, and Other Forces Shape the Southern California Coast.

Meldahl told KPBS Midday Edition on Tuesday that the rising sea level will change California’s beaches.

Centuries ago a person would’ve had to walk another 100 feet to get to the bluffs of La Jolla Cove, he said.

“The sea has been chopping away the land by a large amount,” Meldahl said. “We throw a bunch of homes and businesses at the edge and cement. We’re only postponing the inevitable.”

He said the sea rose by about seven inches in the last century, and he expects it to rise another two to three feet by 2100.

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“We’ve got a problem of shrinking beaches and rising seas,” Meldahl said.

He also warned of the impacts of the coming El Niño.

“The amount of erosion on our beaches is going to be significant again,” he said.

New Book Explores Forces That Shaped California's Coast