Over the last couple million years, glaciers in Colorado and the American West have come and gone to the pace of global climate history. Only 20 thousand years ago we had many glaciers in the state, flowing down the valleys of nearly every mountain range. Yet very few features we would recognize as glaciers now exist in our mountains. I will introduce the history of climate and will discuss what has driven that history over this latest cycle of the ice ages. I will then focus on our own glaciers and how we have come to know their more recent history – chiefly their demise since the last glacial maximum 20 thousand years ago. I will then focus on the hundreds of odd glaciers that now dot our mountain valleys. These “rock glaciers” are cloaked with a layer of rocks that serves as something of a parasol to protect them from the heat, and at the same time prevent them from being recognized as glaciers. We are only now coming to understand how these glaciers work. I will show that a combination of modern speeds from feature tracking and exposure ages from ¹⁰Be concentrations constrains tightly the Holocene climate history of our mountains. Finally, I will use these rock glaciers to document the importance of lateral erosion of the headwalls, generating strong asymmetry of these ranges.

About Dr. Robert Anderson

Bob grew up in Colorado, hiking, photographing and climbing its mountains. Bob went to Williams College in western Massachusetts where he majored in Geology. He then took on a Masters at Stanford, where he was inspired by Arvid Johnson and Bernard Hallet, and wrote a biography of the 18^th century geologist Clarence Edward Dutton under the tutelage of Tjeerd van Andel.

After several years exploring non-academic paths in Colorado and Wyoming, Bob moved to Seattle to the University of Washington to join a geomorphology group there, mentored by Bernard Hallet. He studied the physics of how sand and dust are blown about by wind. That was followed by a two-year postdoc at Caltech working with Peter Haff.

He has been in the teaching-research world of academia since. From 1988 to 2003 he taught at UC Santa Cruz. In that time he veered from the physics of little things like sand grains, and began to research how rivers cut into rock, how marine terraces are etched into rising landmasses (like Santa Cruz itself), and how glaciers that ornament our high country carve out valleys, polish their bedrock, and leave a record of valley occupation in moraines. He and his wife Suzanne, also a geomorphologist, moved to the University of Colorado in 2003, where they have both taught since. They have studied how rocks weather and soils move (a project that Suzanne led) and how glaciers and permafrost evolve in today’s warming world.

In short, Bob is a geomorphologist interested broadly in the evolution of Earth’s surface. He constrains the timing in the landscape (ages of surfaces, erosion rates and residence times) using cosmogenic radionuclides, in particular ¹⁰Be and ²⁶Al.  And he bridges the gap between short-term modern processes and long-term landscape evolution using numerical models that incorporate both our understanding of geomorphic processes, and how they have changed through time as climate swings between glacial and interglacial end-members.

For the Zoom information, please get in touch with Jannis Simões-Seymens (jseymens@stanford.edu)