A glowing full moon peaks through the clouds. The temperature plummets. I rummage through the coat closet in search of mittens, hats, and winter jackets. I pile my family into the car for the hour drive to Westcave Discovery Center near Austin.

I have been looking forward to the December Full Moon Hike for months. I am writing about listening and seeing, about silence and darkness in karst, and I am curious about nocturnal sounds.

I hope we are able to descend the steep and winding trail that leads to the canyon and the grotto and the cave, but I think the afternoon rain will make the stone steps too slippery.

I grew up in Northern Virginia, a place where winter was a time to await the snow. Things are different here in Texas: winter is a time to await the butterflies.

The last week has been filled with unusually warm days and the plants are celebrating. Salvia, skeleton leaf goldeneye, and Copper Canyon daisies receive attention from clouds of insects, it seems. The garden sings. It amazes me every year. Just when I think I should be cutting things back and preparing for the winter, the yard springs to life.

If you've ever visited Spring Lake, you probably explored aboard a glass- bottom boat. Since 1945, the boat ride has been a quintessential San Marcos activity. This fall The Meadows Center for Water and the Environment is also offering kayak trips. I jump at the chance, making a reservation months in advance.

On a beautiful fall morning, near the headwaters of the San Marcos River, over 200 springs gurgle on the bottom of the lake. They look like sandy craters. Because the lake is spring fed, the water is crystal clear. I glide over the surface. I can see all the way to the bottom as I peer over the edge of the kayak. It is mesmerizing.

At one of the larger springs, called Cream of Wheat, white sand appears to bubble up from the depths. Under pressure, the water is expelled from the Edwards Aquifer, the rocky subterranean place where water is stored. Springs are common in this part of Texas and along with limestone caves, disappearing rivers, and sinkholes, they make up an ecosystem known as karst.

Early morning storm clouds descend on San Marcos, Texas. The wind begins blowing, rattling maps and poster board-sized photographs that are being loaded into the van. A handful of geologists, biologists, and cavers huddle nearby, running to their cars now and then to gather additional layers as the temperature drops into the low fifties.

It is field trip day, part of the 2021 National Cave & Karst Management Symposium. This is the day I have been dreaming about for months. . . really. The trip is being led by Dr. Nico Hauwert and is titled "Finding Caves in North Hays County: Recognition of Caves in an Environment Of Widespread Filling."

I watch as caving equipment is placed in the van. Helmets. Rope. Okay, I have been obsessed with subterranean ecology for three-and-a-half years. I have visited many caves, show caves with lit pathways and staircases. I have been searching for caves on my own property. But I am terrified of entering a wild cave. I think I am claustrophobic. I have a fear of heights. I am nearly fifty years old and not in the best shape of my life. Despite my racing heart, I secretly hope this group of fearless explorers will finally get me into a wild cave.

Fall is the time for migration, the last hurrah for many of the creatures in my yard. There are three fall-bloomers that, for me, signify the arrival of fall - maximillian sunflower, frostweed, and goldenrod. But not everyone loves them as much as I do. Sometimes they are referred to as weeds, and my heart sinks. They are tall, taller than me, and lanky. They grow in large clumps, and they spread. They don't stand up straight, especially after a storm. They are wild.

In a cave, human senses are altered. Sight is no longer as important. Sound, smell, touch rise to the surface, relaying information to the body and mind. My experiences in caves have changed me in many ways over the past three years. I have learned from deep silence.

Over the weekend, I attended my first concert in a cave. Joseph Kuipers and the Texas Cellos performed in the Throne Room deep within the Cave Without a Name in Boerne, Texas. The sound of twelve cellos, a cello choir, echoed and reverberated throughout the rock walls. Stunning.

Millions of Mexican free-tailed bats swirl in an ever-rising vortex before me. Their wing-beats sound less like flapping and more like the steady thrum of rain on rooftops. Beyond spectacular, the moment feels celebratory. I sit in awe. The emergence, from the mouth of a cave deep within a sinkhole, will take more than three hours.

This is the largest bat colony in the world. The two-chambered cave sits within a preserve on the northeastern edge of San Antonio, less than thirty minutes from my house. Bat mothers migrate from Mexico every March to have their babies here, one pup per female, and they stay until October. Bracken is a maternal colony. The males form bachelor colonies, like the one at Devil's Sinkhole in Rocksprings, Texas.

Soon whispers of an approaching thunderhead float across the small gathering. There is an energy in the air tonight that holds me in the moment, dreamlike. By the time I leave, flashes of lightening illuminate the purple-black sky. I roll down the window to hear the rumble of thunder. Everything is unusually still or maybe I sense the absence of fluttering bat wings, something I never knew before.

This morning a flutter caught my eye. On the driveway, I found an enormous polyphemus moth, one of the largest silk moths. I called to my son to join me. He is obsessed with Greek mythology and this gorgeous creature was named for a giant cyclops. The two owl-like eye spots on the hind wings scare away predators, I'm sure.

As I gently lifted the moth, its wings covered the span of my cupped hands. I moved it out of the driveway into the leaf litter nearby. Lost in the fallen leaves, we marveled at its ability to camouflage itself.

Not too long ago, I visited a place for the first time, and it felt like I had been there before. I had to figure out what was waiting to be learned from Enchanted Rock. Last week I had an entirely different experience: I visited a place that I immediately knew I would return to over and over again.

Indescribable secrets lay hidden in the landscape, and I couldn't  wait to start my own exploration. For almost three years, I have been obsessed with rocks, more specifically, with cracks and crevices and holes and all of the plants and animals that call those places home. At Westcave and Hamilton Pool, two places located a mile apart near South Austin, the terrain couldn't be more intriguing for someone like me, so full of layers. Layers of rocks and layers of plants lead to hiding places galore and endless possibilities for discovery.

It was a summer of amazing places and beautiful sights, close to home and far away. In Texas, my yard, mini-river, and pollinator garden were filled with life: mating monarchs and Gulf fritillaries, a diversity of caterpillars, a fawn, frog eggs, several nests, and damselfly and dragonfly eggs.

In Maine, I joined the Landscape of Change project as a citizen scientist. Several organizations are working with the community to compare changes in plant and animal populations over time on Mount Desert Island. For comparison, they are using old field logs kept by the the Champlain Society, a group of young men and women who spent their summers on MDI. I have noticed a change in the intertidal zone at our family cabin, and so I am curious to examine the results of this project, as well.

The fungi, lichen, and mosses captured my heart this year. It had been a wet spring and the woods seemed to be filled with these organisms at every turn. Using iNaturalist, I was able to learn about many new species.