One of the most notable aspects of the Vasquez Rocks area in Agua Dulce is the remarkable geology.

Surprisingly, the famous and highly recognizable Vasquez Rocks were created through a relatively simple process. The rocks are made of sandstone which, as its name suggests, is stone made of sand. It is a sedimentary rock formed by deposits of sand and gravel eroding down from the San Gabriel Mountains.

Millions of years of weather and pressure have caused the sand to compact and form flat layers of hard sandstone. Due to their location along the Elkhorn Fault, an offshoot of the San Andreas Fault, the rocks are subject to movement, which has resulted in their extreme lift, with some rocks now sitting at an angle up to 50 degrees, forming what we call “hogs back ridges” after their jagged or sometimes “spiny” appearance.

Photos by Sarah Brewer Thompson

Because these layers were formed over long periods of time and under varying conditions, they differ in color and texture. Some layers are fine-grained, while others, known as conglomerates, contain rocks ranging from small pebbles to larger boulders. The combinations of these different textures and colors result in the fascinating layer-cake look of the formations in the park and allow us to see the angles at which previously connected layers have jolted away from one another.

As one can imagine, they are not a small or young geological feature. The rocks go approximately 4 miles down into the earth and are approximately 25 million years old.

Hat Rock

As with anything of such an ancient age, they have persevered but are always changing. Exposure to the elements breaks and shapes the rocks, which completes the circle and eventually turns them to sand once again. Through erosion, the rocks grow smaller as centuries pass, and they become rounded and smoothed from wind, rain and being climbed upon.

Next time you are at the park, take a moment to appreciate the history of these rocks and imagine the journey they have undergone to become the icons that they are today. It’s fun to think what the rocks looked like 100 years ago, 500 years ago, 1,000 years ago and beyond. They have seen a lot of change over their lives and are sure to see much more.

One of the other fun features of the rocks at Vasquez is the different shapes and forms they make. There are all types of shapes all over the park – faces, cartoon characters, hats, animals and whatever else you can imagine.

Take a look around the park and see if you can find any of the fun shapes hidden in the rocks. Some might be right in front of your nose.

Sarah Brewer Thompson was born and raised in Agua Dulce, where she learned to love and appreciate nature and history. She is a master’s student at California State University, Northridge, and a docent at Vasquez Rocks Natural Area Park. Her areas of interest are local history, archaeology and animal studies.