Short Wave (NPR)

Episode: The Secrets Everyday Rocks Keep

Date: November 4, 2025

Host: Sydney Lufkin (guest hosting)
Guest: Anjana Katwa, geologist and author

Episode Overview

This episode dives into the hidden stories and profound influence of rocks on our planet and human life. Guest geologist Anjana Katwa discusses how the slow, ancient processes of geology underpin everything from the Manhattan skyline to the coffee in your cup. Drawing from her new book, The Whispers of Rock, Katwa weaves together scientific insights and Indigenous narratives to reveal how our landscape, science, and culture are deeply shaped by the secrets locked away in everyday stones.

Key Discussion Points & Insights

1. Rocks and the Shape of Cities

• Manhattan’s Skyline
  • Katwa explains that New York’s skyscraper clusters (midtown and downtown, not in between) are rooted in the hard Manhattan schist—ancient bedrock, the eroded roots of mountains formed 500 million years ago.
    • “As these two continents collided, the landscape was transformed into towering mountains.” — Anjana Katwa [00:57]
  • These geological stories are visible in cities, reflecting deep time beneath our feet.

2. Rocks as Story Keepers

• How Rocks Hold Earth’s and Humanity’s Stories
  • Katwa describes rocks as “ancient storykeepers of time, but also memory keepers of the experiences that we had as we've interacted with them, they take on a whole new life and meaning.” [04:20]
• Culture and Geology Intertwined
  • Indigenous tales, such as the Cherokee Nation’s legend of the great buzzard shaping mountains and valleys, are highlighted as examples of cultural interpretations of geological phenomena. [02:20]

3. A Close Look at Ancient Rocks

• Louisian Gneiss as a Window Into Deep Time
  • Katwa describes holding a pebble from the Isle of Iona (Louisian gneiss, 2.7 billion years old) and explains how rocks like this record Earth's infancy. [05:06]
  • Scientists use the crystal zircon inside such rocks to date their formation, leveraging radioactive decay.
    • Zircon is described as “the superhero of minerals.” [05:56]

4. Earth’s Earliest Environment

• What Early Earth Looked Like
  • The oldest rocks (4.4 billion years) formed when Earth was “a heaving mass of semi molten magma [...] hell on Earth […] a world that was very hot, very unstable [...] devoid of any life forms, and water hadn’t yet quite arrived.” [07:02]

5. Tectonic Plates: Discovery and Impact

• Modern Understanding of Plate Tectonics
  • The structure of Earth’s plates is likened to “a jigsaw.” Continental plates are buoyant, oceanic plates are thinner and denser; their interactions cause earthquakes, volcanoes, and tsunamis. [08:41]
• Mid-Atlantic Ridge & the Seafloor Spreading Revelation
  • Pioneering work by Marie Tharp and Bruce Heezen in the 1950s revealed the mid-Atlantic ridge—evidence for plate tectonics as they mapped ridges and observed “zebra stripes” of reversed magnetic polarity in rocks.
    • “Navigators saw something so strange happening. With their compass needles, they were flicking backwards and forwards… picking up the changing polarity of the rocks that were deep beneath them.” — Anjana Katwa [09:40]

6. Rocks Shaping Human History: The Case of Chalk

• Chalk’s Role in the American South
  • Chalk, described as “holding death in the palm of my hand”—composed of billions of dead microorganisms—weathered into the Black Belt’s fertile soils. These soils enabled cotton plantations, which shaped the demographics and politics that are still visible in voting patterns today. [10:42]
    • “We still see a reflection of that geological belt of chalk, reflected in the voting patterns and reflected in the demographics of the region.” — Anjana Katwa [11:57]

7. Lessons for Our Future

• Why Geology Matters Now
  • Katwa emphasizes that “rocks are extraordinary storykeepers of this wisdom, and when we look at them, we can understand that life is actually a cycle of creation and destruction.” [12:25]
  • She warns that rocks, while appearing solid and stable, are vulnerable: “Once we modify them, once we extract them from the Earth, their story is gone forever.” [13:18]

Notable Quotes & Memorable Moments

• On Rocks as Storykeepers:
  • “For me, the rocks are ancient storykeepers of how our Earth evolved. But they also contain human experiences.” — Anjana Katwa [04:20]
• On the Power of Chalk:
  • “Chalk is such an incredible rock… I feel like I'm holding death right in the palm of my hand.” — Anjana Katwa [10:42]
• On Early Earth:
  • “4.4 billion years ago, the Earth was a heaving mass of semi molten magma… hell on Earth.” — Anjana Katwa [07:02]
• On the Vulnerability of Rocks:
  • “Once we modify them, once we extract them from the Earth, their story is gone forever.” — Anjana Katwa [13:18]

Key Timestamps

• Manhattan’s Bedrock and Skyscrapers: 00:21–01:42
• Indigenous Story – Great Buzzard legend: 02:20
• Rocks as Storykeepers: 04:20
• Louisian Gneiss and Zircon: 05:06–05:56
• Dating the Oldest Rock: 06:41–07:02
• Tectonic Plate Explanation: 08:41
• Marie Tharp, Bruce Heezen, and Plate Tectonics: 09:40
• Chalk and the Black Belt: 10:42–11:57
• Why Rocks Matter Now: 12:25–13:18

Episode Closing

• Anjana Katwa’s book, The Whispers of Rock, is out now.
• Host Sydney Lufkin thanks Katwa for joining the show. [13:36]
• Episode production credits (Burleigh McCoy, Brent Baughman, Tyler Jones, Robert Rodriguez, Beth Donovan). [13:48]

This episode invites listeners to see rocks not as inert background objects, but as the ancient, living narratives upon which all of human civilization—and its future—are built.