Hortensia de los Santos
Author, Researcher, Theorist

Dual Impactor Theory

A New Analysis on the Chicxulub Asteroid Event

The Dual-Impactor Hypothesis: A Paleo-Geological Perspective on the K-Pg Extinction, Pacific Tectonic Shifts, and the Acceleration of the Indian Plate By Hortensia de los Santos BS

• Abstract

  Here I propose a dual-impact hypothesis as a significant driver of geological and biological transformations around 66 million years ago (Ma).

  I argue that the Chicxulub impactor, long associated with the Cretaceous-Paleogene (K-Pg) mass extinction, was a fragment of a much larger celestial body, whose main mass impacted the Pacific Basin.

  This Pacific impact, now buried beneath oceanic sediments, could explain:

  • The formation of the modern Pacific Basins' crustal thinning and tectonic anomalies
  • The onset of the Ring of Fire subduction zones
  • The anomalous acceleration of the Indian Plate toward Eurasia (~100 to 50 Ma)
  • The long-term cooling trends post-K-Pg, possibly contributing to a global Iceball Earth scenario
  • The formation of a tectonic rift in what is now the Grand Canyon region

  This hypothesis suggests that the K-Pg extinction event was not solely the result of the Chicxulub impact but rather a planetary-scale event caused by a dual impact scenario.

  1. Introduction

  The K-Pg boundary (~66 Ma) marks one of the most catastrophic mass extinctions in Earths history, responsible for the demise of the non-avian dinosaurs and the collapse of Mesozoic ecosystems. While the Chicxulub impact (Mexico) remains the leading explanation for this event, additional evidence suggests that a second, larger impact in the Pacific Basin may have played a fundamental role in shaping the planet's tectonic and climatic history.

  The Pacific impact may have:

  • Altered mantle convection, triggering rapid tectonic movements
  • Initiated long-term volcanic activity that fueled the Deccan Traps
  • Contributed to deep-sea sedimentary disruptions consistent with impact-generated megatsunamis
  • Accelerated India's movement toward Eurasia, leading to the collision that formed the Himalayas

  Here, we explore the geological evidence supporting this dual-impact model and its far-reaching consequences.

  2. Evidence for a Pacific Basin Impact

  A large-scale impact in the Pacific region would have had profound consequences for Earth's crust and mantle dynamics. While no confirmed Pacific crater has been identified, several geological anomalies hint at such an event.

• A. Crustal Thinning and Mantle Disruption
The Pacific Basin exhibits an unusually thin oceanic crust in certain areas, inconsistent with typical mid-ocean ridge formation models.
A high-energy impact event:
• Could have penetrated deep into the mantle, removing large amounts of substrata
• May have influenced hotspot volcanism, possibly linked to the formation of Shatsky Rise (~145 Ma) and the Ontong Java Plateau (~120 to 80 Ma)
• B. Gravity and Seismic Anomalies
Regions of the Pacific Ocean floor show gravitational inconsistencies, suggesting a buried impact basin. Seismic studies reveal mantle upwellings beneath the Pacific Superswell, potentially indicative of a mantle disturbance caused by an impactor.
• C. Global Stratigraphic Signatures
The K-Pg boundary layer found in marine sediments worldwide contains:
• Iridium anomalies (a marker of extraterrestrial impacts)
• Shocked quartz and tektites, typical of high-energy impacts
Deep-sea sediment disruptions, possibly linked to a megatsunami event

3. The Chicxulub Impact: A Secondary Fragment?

The well-documented Chicxulub crater (~180 km in diameter, Yucatán Peninsula) resulted from a ~10 km asteroid, which alone could not account for all the geological and biological consequences of the K-Pg event.

If Chicxulub was merely a fragment of a much larger parent body, then:
• The main impactor could have struck the Pacific Basin.
• The force of this dual event would have been far greater than previously estimated.
• The global environmental effects would have been prolonged, leading to extended climate disruption.

4. The Impact's Role in Accelerating India's Plate Movement

A key mystery in plate tectonics is why the Indian Plate moved anomalously fast (~15 to 20 cm/year) toward Eurasia between 100 and 50 Ma, a speed unmatched by any modern plate movement.

A Pacific impact could explain this acceleration.
• A. Mantle Convection Disruption
  • A deep mantle penetration event in the Pacific could have altered subduction dynamics in the Tethys Ocean.
  • This would have weakened resistance beneath the Indian Plate, allowing it to move northward at an accelerated pace.
• B. Deccan Traps Volcanism and Mantle Plumes
  • The impact could have destabilized the Indian mantle plume, intensifying the Deccan Traps eruptions.
  • This would have contributed to greenhouse gas release, exacerbating climate stress at the K-Pg boundary.
• C. Slowing of Indian Plate After Collision (~50 Ma)
  • Once India collided with Eurasia, the plate slowed to ~5 cm/year
  • This led to the formation of the Himalayas and Tibetan Plateau, further altering global climate through silicate weathering and CO₂ removal.

5. The Formation of the Ring of Fire and the Grand Canyon

• A. Pacific Subsidence and the Birth of the Ring of Fire
  • The loss of substrata in the Pacific Basin caused mass subsidence of the western edge of North America. This event set the stage for subduction zones, forming the Ring of Fire.
• B. The Grand Canyon as a Rift Structure
  • As the Pacific Plate pulled away and subsided, it created tensional stress in the interior of North America. This may have formed a proto-rift valley in what is now Arizona, which later became the Grand Canyon.
  • Over time, uplift of the Colorado Plateau deepened the rift, shaping the canyon as we see it today.

6. Climatic Consequences: The Iceball Earth Hypothesis

The ejection of aerosols from both impacts would have triggered extreme cooling. This may have initiated or prolonged a Snowball Earth-like state, contributing to:

• Ocean acidification
• Mass extinctions beyond just dinosaurs
• Delayed recovery of ecosystems in the early Paleocene

7. Conclusion

This dual-impact hypothesis provides a more comprehensive explanation for:

• The K-Pg extinction and its prolonged aftermath.
• The Pacific Basin's unusual geological features.
• The Ring of Fire's origins.
• The rapid movement of the Indian Plate toward Eurasia.
• The formation of the Grand Canyon as a rift valley.
• The possibility of an Iceball Earth scenario triggered by impact ejecta.

Future Research Directions

• Seismic imaging to locate a buried impact crater in the Pacific.
• Geochemical analysis of deep-sea cores for evidence of a second impact.
• Mantle convection modeling to test the impact's effects on plate motion.

If confirmed, this hypothesis would redefine our understanding of the K-Pg event and its role in shaping the modern Earth.