Exposed!

MOTHER Nature has a gift next week for Southern California beachcombers -- the best tide pooling of the year.

Pools and rocky crevices along the shore regularly fill when waves sweep across California’s coastlines. When the water recedes, those pools are left teeming with sea creatures. And the lower the tide, the more diverse the life within the pools.

Because of an unusual combination of natural events, low tide will be lower than usual from Dec. 22 to 24, creating wide expanses of exposed beach during daytime.

What’s so great about the lowest of the low? “You’re getting a rare glimpse of things that are subtidal -- what scuba divers and snorkelers see,” says Scott Rugh, a biologist at the San Diego Natural History Museum.

“These are good conditions for having as strong a tide as you can get around here,” says Tony Cook of Griffith Observatory. That includes a string of “minus” tides -- those below the average low tide -- including a super-low minus 2-foot tide in La Jolla on Dec. 23 at 3:41 p.m. (An average low tide is about a foot above the average water line.)

The most extreme high and low tides usually occur between November and February, due to a combination of astronomic and hydrologic events. One of those events is the spring tides, which occur when there is a new and a full moon. Their name represents the yo-yo effect of the seas springing out and back -- and they create a stronger gravitational pull on the ocean than at other times of the year.

In addition, the moon drives the tides while the sun plays a lesser role. The big tidal swings are caused by a combination of a new moon’s strong gravitational pull; the alignment of Earth, sun and moon, which also causes a stronger pull; and the moon being at the closest point to Earth during its orbit, which also strengthens the moon’s hold on the sea.

It’s much more common during such tides to see a diversity of sea life, including sponges, sea stars, octopus and lobsters.

When a tide gets to minus 1.7 feet on the West Coast, “You gotta go,” says Linda Chilton, an education specialist at Cabrillo Marine Aquarium in San Pedro, home to tide pools at Point Fermin Marine Life Refuge. (The aquarium conducts guided tours of the tide pools.)

Biologists assign numbers to the tidal zones along the coast because each zone has sea life that has specifically adapted to it. For example, zone 1, the splash zone, is mostly dry, with rocks that receive little more than a splatter from waves during high tide. In this zone, snails, limpets and barnacles seal in moisture by clamping onto rocks.

Farthest from shore is zone 4, the seldom exposed subtidal area that next week’s minus tides will reveal.

Surf grass -- which is almost always underwater -- is one indication that tide enthusiasts have hit the treasure trove of zone 4. In some areas, tide poolers can follow the line of surf grass and carefully uncover jewels like brittle stars hiding underneath rocks.

The best tide pools stretch along rocky shorelines from Central California south through San Diego.

The most popular include those at Montana de Oro State Park, Carpinteria State Beach, the coast of the Palos Verdes Peninsula, Leo Carrillo State Beach, Laguna Beach, La Jolla and Torrey Pines State Beach and Reserve.

Too much trampling is bad for the tide pools, so visitors should wear sneakers, step lightly and not remove marine life. If you do move a rock to ogle what’s underneath, remember that it’s best to look but not touch -- then put the rock back exactly where you found it.

To e-mail Julie Sheer or read her previous Outdoors Institute columns, go to latimes.com/ juliesheer.