Brian A. Clarke

• PhD
• Principal at Geomorphic Science Solutions

Bedrock fracturing and rock strength are widely believed to influence landscape morphology and erosional resistance. Yet, understanding of the quantitative relationship between rock-mass strength and landscape evolution remains limited. Here we present a new application of seismic refraction surveys that uses variations in seismic velocity to inter...

The role of bedrock fractures and rock mass strength is often considered a primary influence on the efficiency of surface processes and the morphology of landscapes. Quantifying bedrock characteristics at hillslope scales, however, has proven difficult. Here, we present a new field-based method for quantifying the depth and apparent density of bedr...

The relationship of sediment flux to surface slope is a predominant control on the evolution of transport-limited hillslopes. Although both linear and nonlinear sediment flux models have been proposed and widely debated, this functional relationship remains one of the outstanding questions in geomorphology. We examine degradation of fluvial terrace...

Prior numerical modeling work has suggested that incision into sub‐horizontal layered stratigraphy with variable erodibility induces non‐uniform erosion rates even if base‐level fall is steady and sustained. Erosion rates of cliff bands formed in the stronger rocks in a stratigraphic sequence can greatly exceed the rate of base‐level fall. Where qu...

Every year, natural petroleum seepage emits 0.2-2Tg of oil to the ocean. Significant oil seepage can build large underwater mounds, consisting of tar deposits with morphologies similar to volcanic lava flows, known as asphalt volcanoes. Such events are typically accompanied by large fluxes of the greenhouse gas methane. Marine sediments from the Sa...

The mechanisms by which climate and vegetation affect erosion rates over various time scales lie at the heart of understanding landscape response to climate change. Plot-scale field experiments show that increased vegetation cover slows erosion, implying that faster erosion should occur under low to moderate vegetation cover. However, demonstrating...

Stable-isotope data and modeling studies have focused on establishing a relationship between elevation and the δ18O and δD of precipitation in order to interpret paleo-isotope data in terms of past moisture sources and changes in the distribution of rainfall. Far less is known about how local topographic features such as the height and relief of or...

Quantifying paleoclimatic conditions and past climate change is fundamental to advancing understanding of the Earth's climate and improving our ability to predict future climate change. Glacial records provide a means to constrain the timing and magnitude of past climate change within the terrestrial realm and can be integrated with other paleoclim...

Changes in climatic or tectonic forcing alter the efficiency and intensity of geomorphic processes and drive punctuated variability in rates of erosion as landscapes adjust to changing boundary conditions. Changes in climatic forcing, however, generally occur more frequently and over significantly shorter timescales than variations in tectonic forc...

Bedrock fractures and rock-mass strength play a primary role in governing landscape morphology and the efficiency of surface processes. Quantifying bedrock characteristics at hillslope scales, however, has proven difficult. Here, we present a new field-based method for quantifying bedrock fracture densities within the shallow subsurface based on se...

The role of bedrock fractures and rock-mass strength is often considered a primary influence on the efficiency of surface processes. Quantifying bedrock characteristics at hillslope scales, however, has proven exceedingly difficult. Here, we present a new field-based method for quantifying bedrock fracture densities within the shallow subsurface ba...

The Southern Alps and Fiordland ranges of New Zealand are both characterized by landslide dominated erosion. Though both ranges experience similarly high rates of rainfall (>12m/yr) and have similar climatic histories, rates of erosion are up to twenty-times greater in the Southern Alps. The bedrock compositions of the two ranges differ considerabl...

Landscape evolution in collisional orogens is predominantly driven by spatial and temporal patterns of climatically induced differential erosion in concert with tectonic forcing. Here we investigate the influence of climate, lithology, topography and the primary erosive processes on the landscape morphology of Fiordland, South Island, New Zealand....

An orogen's geometric form is the result of the competition and balance between tectonic uplift and climatically induced erosion. We examine the relationships between present-day orogenic form, climatic gradients, and spatial patterns of denudation derived from low-temperature thermochronology and cosmogenic radionuclides (CRNs) to interpret the te...

River-cut terrace risers form at a known initial geometry. Their subsequent degradation, from down-slope transport of sediment, is an aggregate of hillslope processes, mainly attributed to particle-by-particle gravitational unraveling and biological disturbances. This study examines the ability of linear, non-linear, and geometric models to quantif...