As you read this, I’m headed home from GSA Connects in San Antonio, Texas. What a great week! It was wonderful to meet so many new colleagues at the AAPG booth in the convention center. In between interesting talks and poster sessions, I was able to fit in some local geo-sites, right near the famous Riverwalk. Let’s go see! 🌮🤠
Sharon Lyon
Editor, GeoLifestyle
The Alamo, San Antonio, Texas
The Alamo Church; Mollusks in the limestone blocks of the Convento Courtyard.
The Alamo is a UNESCO World Heritage Site and one of the most-visited landmarks in Texas. Located near the San Antonio River Walk, it tells the legendary story of the 1836 Battle of the Alamo.
History: Founded in 1718 as Mission San Antonio de Valero, the Alamo was the first mission in San Antonio. It served as a stop for travelers between East Texas and Mexico.
The Alamo was strategically placed near the San Antonio River for its abundant spring-fed water.
In 1836, about 200 Texan defenders, including William B. Travis, James Bowie, and Davy Crockett, held the Alamo against General Santa Anna’s 2,500 Mexican troops.
The 13-day siege ended in defeat for the Texans, but their courage inspired the rallying cry “Remember the Alamo!” The spirit of the event fueled the Texas Revolution and the creation of the Republic of Texas.
Over time, the site evolved from a mission to a U.S. Army Quartermaster Depot warehouse and finally a memorial to the defenders.
Geology of the Alamo’s structure: The Alamo’s limestone blocks were quarried from the Atco and Vinson Formations, part of the Austin Chalk Group, in the San Antonio area.
The formations were deposited near the southern end of the Western Interior Seaway in the late Cretaceous, 80–90 million years ago.
The lime mudstone used in construction gives the Alamo’s walls their characteristic texture and pale hue.
Fossils of mollusks can be seen within the limestone blocks.
Admission to the Alamo Church (Shrine) is free, but timed reservations are required for entry. There is a charge for the exhibit halls.
The Sacristy Exhibit offers an immersive timeline of the Church’s transformation through the centuries.
The Ralston Family Collections Center houses more than 500 artifacts from multiple collections. Once the new museum opens in 2027, these artifacts will move there, and the Collections Center will host traveling exhibits.
Visit the Living History Encampment behind the Church to meet historians demonstrating 1830s daily life—from fire-starting and leatherworking to health care and firearm care.
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Map, Glen Tilt, Tayside (One of the Lost Drawings of James Hutton).
Often referred to as the Father of Modern Geology, James Hutton was a Scottish geologist, physician, and naturalist. His key work, Theory of the Earth, was published in 1788 and expanded in 1795.
Hutton may be best known for Uniformitarianism: the idea that the same natural processes that shape the Earth today operated throughout geologic time. It is summarized by the phrase “the present is the key to the past.”
Recognizing that these processes require vast spans of time (now known as “deep time”), Hutton concluded that there was “no vestige of a beginning, no prospect for an end.”
Hutton was a proponent of plutonism, arguing that many rocks were formed from molten magma rather than from oceanic precipitation.
He recognized the importance of unconformities and used them as evidence of immense gaps in time and cycles of uplift and erosion. The angular unconformity at Siccar Point, Scotland, is one of his famously studied outcrops.
The Briscoe Western Art Museum showcased for GSA Connects attendees The Lost Drawings of James Hutton in honor of his upcoming 300th birthday (June 3, 2026).
The exhibition allowed us to view original illustrations created for Hutton’s Theory of the Earth. The illustrations were never published because Volumes 3 and 4 remained unfinished when Hutton died in 1797.
Most were drawn by Hutton’s close friend John Clerk of Eldin. Two were drawn by another associate, James Hall.
The drawings were lost for centuries and rediscovered in 1968. Twenty-nine facsimiles were produced from the originals, and one set was on display at the Briscoe Museum.
The featured works include outcrops at Siccar Point, Edinburgh, and the Isle of Man.
A commemorative trail: The Scottish Geology Trust, Edinburgh Geological Society, and the James Hutton Institute are establishing a Deep Time Trail at Siccar Point in time for the Tercentenary. Their crowdfunder for this endeavor runs until the end of November. The trail will explain the significance of the site and of Hutton’s work.
Naylor Family Dinosaur Gallery; Deinosuchus riograndensis, giant alligator relative of the late Cretaceous.
Located in Brackenridge Park, along the San Antonio River, the Witte Museum is dedicated to sharing the story of Texas from prehistory to the present.
Trip tips: Start in the Valero Great Hall, aglass-enclosed entry hall with life-size replicas of an Acrocanthosaurus, Tyrannosaurus rex, and a Quetzalcoatlus with a 40-foot wingspan.
The Naylor Family Dinosaur Gallery is a journey into Texas’s Cretaceous Period, featuring fossils, footprints, and reconstructions of ancient ecosystems.
The Kittie West Nelson Ferguson People of the Pecos Gallery explores 9,000 years of human history in the Lower Pecos Canyonlands through artifacts, rock art, and multimedia displays.
Learn about the region’s cultural and economic history, including cowboy life, oil and gas discovery by Petty Geophysical, and 19th-century San Antonio in the Robert J. & Helen C. Kleberg South Texas Heritage Center.
Why it matters: The Witte Museum provides a journey through time—from the prehistoric age to the contemporary era—reflecting the cultural, natural, and artistic heritage of Texas.
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