EVIDENCES FOR RAPID FORMATION AND FAILURE
OF PLEISTOCENE “LAVA DAMS” OF THE
WESTERN GRAND CANYON, ARIZONA

Presented at the Fourth International Conference on Creationism
Pittsburgh, PA, August 3-8, 1998

KEYWORDS

Arizona, Grand Canyon, catastrophic erosion, dam breachment, lava dam, geomorphology, excess argon, K-Ar dating, Pleistocene Epoch.

ABSTRACT

Over 200 isolated outcrops of horizontally stratified, basaltic lava flows within the inner gorge of western Grand Canyon indicate that several natural “lava dams” blocked the flow of the Colorado River during the Pleistocene, resulting in the formation of several lakes within the canyon. The largest lake was 90 m above the high water level of present-day Lake Powell and backed up a distance of over 480 km to Moab, Utah . Although early studies indicated that three or less dams once blocked the inner gorge, work completed in 1994 indicated that at least 13 distinct lava dams may have blocked the Colorado River. Comparison with modern erosion rates of cliff retreat (Niagara Falls) indicate that the 13 dams would have required a minimum of 250,000 years to erode during the Pleistocene. However, geologic features and relationships not previously considered indicate that the dams formed rapidly (hours, days, or months) and failed catastrophically soon after formation. Excess radiogenic argon is contain within many basalts of Grand Canyon. This initial argon invalidates K-Ar model ages which are assumed by many geologists to require an age of more than one million years for the oldest lava dams. We envision that the entire episode of the lava dams can easily be reconciled within a time-frame of less than two thousand years. Our observations and interpretations reveal serious flaws in the current long-age time-scale of the Pleistocene Epoch.

INTRODUCTION

The western Grand Canyon contains a unique and spectacular sequence of Pleistocene volcanic flows. The basaltic flows are particularly captivating because of their stark contrasting jet-black color against the light brown and red hues of the underlying Paleozoic sedimentary rocks. The Pleistocene flows appear as “frozen” lava falls cascading down the walls of the inner gorge to the Colorado River below. They also have a much more unique aspect which was first observed by John Wesley Powell in 1887. Powell noted that many of the inner gorge flows are horizontally bedded, indicating that they once extended across the entire width of the inner gorge, damming the Colorado River and forming an immense lake within the Grand Canyon. Later geologic studies showed that there were possibly several separate lava dams within the western Grand Canyon during the Pleistocene. Recently, W. Kenneth Hamblin [6] evaluated over two hundred lava-dam remnants within the inner gorge between miles 177 and 254 (river miles measured downstream from Lee’s Ferry, Arizona – See Figure 1) and concluded that at least 13 separate and distinct lava dams once blocked the Colorado River spanning a length of time between approximately 1.8 Ma (million years ago) to as recently as 0.45 Ma.

The remnants of lava dams outcrop at elevations from river level (500 m) up to near the top of the inner gorge rim (1200 m),and vary in size from a few meters to over 2.5 km long. The tallest and oldest lava dam had a crest of 700 m above the Colorado River and backed up a lake to near Moab, Utah (a distance of over 480 km) which would have been 90 m above the high water level of present-day Lake Powell. The dams were all at least several kilometers long, with the longest extending a total distance of over 138 kilometers. Based on present rates of retreat of Niagara Falls, Hamblin [6] suggested that the individual dams required from 10,000 to 40,000 years to erode. Using an intermediate value of 20,000 years, Hamblin [6] concluded that the Colorado River would have been dammed a total of up to 250,000 years during the period between 1.8 Ma to 0.45 Ma of the Pleistocene.

Lava dams figure prominently in the rendition of Grand Canyon in the popular press. Hamblin and Hamblin [7] have recounted the naturalist’s common perception of Grand Canyon’s lava dams being “more than one million years old.” Davis Young [17], a Christian geologist writing about Noah’s Flood, has reiterated the notion that Noah’s Flood could not have been involved in forming the Grand Canyon, because the canyon was already present “1.16 million years ago” when lava flowed in and blocked the river. Young’s very precise “age” for the lava dam comes from potassium-argon (K-Ar) dating of the basalt [12].

This long time-frame potentially presents a problem to those who hold to a Biblical view of a young earth and a short time-frame for Earth history. If the Pleistocene is a post-Flood epoch, then the episode of the volcanic dams needs to be reconciled within only a several-thousand-year time-frame, and not the “more than one million years” of the uniformitarian time scale. Does the geologic field evidence support a short or long time-frame scenario for the development and subsequent erosion of the Pleistocene lava dams? We believe that the evidence overwhelmingly supports a short time-frame, and we will examine several important details not previously considered.