Early Jurassic Slab with Raindrops

A large, gray slab of rock features a mottled, undulating surface and a jagged edge.

Raindrops on Sediment, Early Jurassic, Beneski Museum of Natural History, photo by the author.

Description

The Rain on Sediment specimen has a flat, stone surface marked by a constellation of shallow, round impressions that resemble soft dimples or delicate craters. These fossilized raindrop marks are unevenly scattered, giving the surface a textured, almost tactile quality. The stone itself is layered and fine-grained, with natural tones ranging from dusty gray to warm reddish-brown, subtly blending like a weathered canvas. Its surface looks both smooth  and pitted, worn by time but still crisp in detail. In some areas, faint ripple patterns cross the slab, like the remnants of flowing water frozen in place. There are also small, indistinct track-like markings that hint at movement, researchers have concluded of ancient creatures crossing the wet mud before it hardened. This specimen’s appearance is not dramatic in scale or color, but in detail. It rewards careful looking, revealing layers of visual texture that speak to its ancient origin. It is a portrait of a vanished moment, captured not in paint or photograph, but in stone.

Weather 

The sedimentary rock specimen features fossilized impressions of raindrops and possibly hailstones, offering a rare and captivating record of prehistoric weather. These imprints formed millions of years ago when precipitation fell onto soft, exposed surfaces of mud or sand. As each droplet or hailstone struck the ground, it left behind small, rounded depressions. Each one varied in size and depth depending on the intensity of the storm and the consistency of the sediment. In a process known as lithification, these soft sediments were gradually buried by additional layers and compressed over vast periods of time, hardening into rock and preserving the delicate impressions.1 What makes this specimen so scientifically valuable is its ability to capture a specific atmospheric moment, evidence of actual weather events that took place in the distant past. By examining the size, distribution, and orientation of the raindrop marks, researchers can infer details about ancient climates, including storm strength, wind direction, and surface conditions. Some of the deeper indentations may even suggest hail, indicating the presence of strong updrafts and cooler air systems. In essence, this rock acts as a natural fossil of the sky, preserving not just life, but the forces that shaped the environment in which life evolved. It provides a connection to the Earth’s atmospheric history, offering a window into the dynamic and ever-changing patterns of weather long before humans began to record them.2,3

Context 

This specimen was formed in what is now Turners Falls, Massachusetts, during the Early Jurassic Period, roughly 200 million years ago. Rather than being created in a single moment, this sedimentary rock developed gradually over an extended span of time through a series of natural processes. Layers of sediment such as mud, sand, and silt were deposited by wind, water, and changing environmental conditions, accumulating slowly in a dynamic landscape shaped by rivers, wetlands, and shifting shorelines. Over time, these sediments were compacted and cemented together in a process known as lithification, eventually forming solid rock. Embedded within these layers are the preserved imprints of ancient raindrops, hailstones, and even the faint tracks of animals that once moved across the soft ground. These features provide direct evidence of the environmental context in which the rock was formed, capturing not only the weather but also signs of prehistoric life. The fossilized impressions serve as a physical record of Early Jurassic ecosystems and weather patterns, offering an extraordinary glimpse into the conditions that existed in Turners Falls hundreds of millions of years ago.4

Provenance

This object was collected in Turners Falls, Massachusetts, in 1863. Located in the Connecticut River Valley, Turners Falls is now part of a richly diverse natural landscape made up of riverine systems, forested uplands, and wetlands. The Connecticut River, one of the longest and most significant rivers in New England, plays a central role in shaping the region’s ecology and geology. Its seasonal flooding and sediment deposition have long contributed to the formation of sedimentary layers ideal for preserving features such as raindrop and hailstone impressions. The conditions at Turners Falls where water, weather, and sediment interacted over millions of years make it a key site for understanding the region’s prehistoric climate and environmental changes.

Footnotes

  1. “Lithification,” Encyclopædia Britannica, accessed May 9, 2025, https://www.britannica.com/science/lithification. ↩︎
  2. Margaret A. Thomas, ed., Guidebook for Field Trips in Connecticut and Massachusetts (Hartford: State Geological and Natural History Survey of Connecticut in cooperation with the Geological Society of Connecticut, 2012), https://portal.ct.gov/-/media/DEEP/geology/guidebooks/Guidebookno9NEGSA2012pdf.pdf ↩︎
  3. Sanjoy M. Som et al., “Air Density 2.7 Billion Years Ago Limited to Less than Twice Modern Levels by Fossil Raindrop Imprints,” Nature 484 (2012): 359–362. ↩︎
  4. Steve Winters, “Geologic Walking Tour of Turners Falls,” Turners Falls RiverCulture, 2009, accessed May 9, 2025, https://greatfallsdiscoverycenter.org/wp-content/uploads/2020/05/geologic-walking-tour. ↩︎