rramalho | Lamont-Doherty Earth Observatory
Founder of the Wollongong Isotope Geochronology Laboratory and found of isotope geochemistry. Links between landscape evolution, soil development and the global carbon cycle - how does . and water storage potential in the Southern Sierra Critical Zone Observatory . Encyclopedia of Scientific Dating Methods. Proposing Institutions: Lamont-Doherty Earth Observatory, University of Helium Dating Workshop (HeDWaAZ), June Instructor Combining multiple geochronological techniques on detrital minerals to Using detrital thermochronology to constrain long-term landscape evolution, and the thermal. To do this I apply fieldwork, geochronology, terrestrial and airborne LiDAR, and a range of quantitative methods to zones of active crustal deformation. The Landscape Evolution Observatory: a large-scale controllable infrastructure to . Morphologic dating of fault scarps using airborne laser swath mapping (ALSM) data.
Given the complexity of the surface environment, with its interwoven and highly nonlinear physical, geochemical, and biotic systems, it is not surprising that theoretical methods for predicting its evolution are only in their early stages. Intentional scientific experiments in the field are common, but necessarily involve short length and time scales; reduced-scale laboratory experiments are proving to be useful, but they cannot capture all aspects of surface dynamics.
Photo courtesy of Christopher Paola, University of Minnesota. Reflections from deeply buried surfaces were extracted from a three-dimensional seismic volume to produce these maps of ancient seascapes. Bertoni and Cartwright Reproduced with permission of Blackwell Publishing Ltd. Page 40 Share Cite Suggested Citation: We will learn from these experimental results even as we try to predict and perhaps influence them. Yet the increasing influence of humans at global scales impels us to make better use of the roughly 4-billion-year record of natural experiments that have already occurred on Earth.
The record of natural experiments includes extreme events such as meteor impacts and rapid climate changes, as well as states of the Earth—for example, one that is nearly ice-free—that are quite different from the one we know. Now as we put increasing pressure on environmental services, urbanize hazard-prone landscapes, and become predominant geologic agents ourselves, understanding the full range of planetary behavior has become crucial. Numerous other examples of insights gained from studies of surface evolution on a range of time scales are included in other sections of this report.
The archive of Earth history records a far richer range of states and behaviors of the landscape than we can observe directly in the tiny slice of time we occupy today.
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As such, sedimentary and other landscape records can provide critical information about how the landscape could change in the future. Quantitative Reconstruction Interpretation of landscape records by Earth surface scientists to this point has been mostly qualitative.
The crucial next step is to accelerate the process of learning to read these often fragmentary records quantitatively, in order to understand long-term dynamics and reconstruct extreme events and variability and to provide the results in a form that can be used by decision makers. Recent examples of reconstruction include the spectacular findings from ice-core analysis showing that climate can change dramatically see also Section 2.
These inspiring results represent a first step to unlocking the surface and sedimentary archive. Initiatives to study the Paleocene-Eocene Thermal Maximum approximately 55 million years agoan ancient warm interval potentially analogous to an anthropogenically warmed Earth, provide a good example of this approach. The Calamitous 14th Century. Page 41 Share Cite Suggested Citation: Equally importantly, new radiometric and other surface-dating methods Box 1. These tools are precisely those needed to quantify landscape evolution and to reconstruct the path that has led to the present state.
In tectonically active areas, analysis that includes data from these tools can, for instance, extend seismic records to time spans beyond those of human records see also Section 2. In any area, reading geomorphic history quantitatively will allow us to measure fluctuations in key environmental quantities, such as fluxes of sediment and nutrients through Holocene time the last 11, years of Earth historyand to constrain the magnitudes of extreme events see also Section 2.
These essential data provide the natural context for the observed acceleration of anthropogenic changes to the surface environment. Documenting Topography at the Scale of Transport and Erosion Processes Airborne laser mapping began only in the mid s, and the technology has improved rapidly since then.
Stephen B DeLong, Ph.D.
In the National Science Foundation NSF supported the founding of the National Center for Airborne Laser Mapping NCALM to provide research-grade airborne laser swath data to the national research community, to advance the technology, and to provide education and training for students.
By Januarymore than 60 projects covering some 13, km2 had been flown. NCALM makes available the data for all its surveys through its web page http: By the end of its first 10 years, NCALM will have flown about 80 seed projects in support of graduate research, providing key data and contributing to a new generation of researchers advancing the field of Earth surface processes through use of high-resolution topography.
InNSF supported an international workshop on High-Resolution Topographic Data and Earth Surface Processes to explore how high-resolution topographic data can advance understanding of Earth surface processes Merritts et al. Nearly half of the more than 60 participants were graduate students or postdoctoral researchers who had received a doctorate within the past three years.
Page 42 Share Cite Suggested Citation: The confluence of the need to understand and predict the evolution of the surface environment and the availability of large volumes of high-resolution information on the subsurface archive—much of it from the oil and gas industry—provides a new level of motivation to bring these two fields together both to improve prediction in the subsurface and to use the archive to understand how the surface system works.
Another key element is to develop observations and methods that link processes across the range of time scales from the present day to deep time.
Laboratory experiments that, in effect, speed up time are one way of approaching this. These experiments are being investigated intensively for their value in understanding climate dynamics and testing numerical climate models. A glance out an airplane window on a clear day is enough to remind us of the remarkable capacity of landscape processes to create spatial patterns.
These geopatterns comprise a diversity of scales and forms, and most show a fascinating mix of order and disorder. Familiar examples include the treelike, branching patterns of stream networks that create erosional and depositional landscapes; river channels, with their ornate meanders and braids; sand dunes; glacial valleys and landforms; deltas; barrier islands; and the zones and fabrics of soils Figures 2. Physical landscape patterns are often closely associated with biotic ones, ranging from the variation in forest type with upland elevation to riparian ecosystems tied to stream channels to the exquisite control of marsh vegetation by small changes in land elevation and wetting frequency.
These include cultivated areas with simple geometric boundaries quite unlike the intricate patterns of natural landscapes, as well as cities and towns that may exhibit locally regular spatial structures. New kinds of surface geopatterns appear as we explore landscapes that are new or are on unfamiliar scales. For example, advances in sonar and other underwater imaging techniques have enabled us to visualize underwater landscapes as if from an airplane, revealing spatial patterns on the seafloor that often appear to be scaled-up cousins to their terrestrial counterparts Figure 2.
Page 43 Share Cite Suggested Citation: These and many other geopatterns arise through local interactions and structure the landscape. What do they tell us? The image on the left shows patterns in a mountain and valley landscape on the border of China and Myanmar, while the image on the right shows the sinuous and branching patterns present at the mouth of the Kayan River, Indonesia. Microscopic imaging has also revealed patterns of mineral dissolution at micron scales that are similar to those developed on the scale of landscapes.
Measurement of molecular biological signatures has revealed the details of spatial patterns, recognized for decades, in the distribution of biota as a function of depth and position in soils and sediments see also Section 2.
Satellite images of other bodies in the solar system also reveal geopatterns that show familiar forms developed in unusual materials and under conditions different from those on Earth.
Most of the natural geopatterns we see are self-organized—they emerge spontaneously from local interactions as opposed to being imposed by some outside influence. Patterns that arise from the internal dynamics of landscapes are autogenic, a term that encompasses both spatial and temporal variation. Most geopatterns, regardless of scale, are also dynamic—they develop over time and in many cases remain dynamic even when statistically in steady state.
Natural geopatterns are also resilient. Where do these patterns come from? How can we use them? As old as these questions are, new observational and analytical methods are now available to yield deeper answers to them.
Page 44 Share Cite Suggested Citation: Their characteristic scale is much greater than that of the waves that create them. The striping results when biogeochemical processes cause electrons to be transferred to metal oxides containing iron and manganese. The bars represent downward depth in the soil profile. The top bar is at 1. Page 45 Share Cite Suggested Citation: Even someone unfamiliar with central-pivot irrigation systems would have no trouble identifying this pattern as unnatural.
Central-pivot irrigation systems tap subsurface groundwater. Each circle can be very large—51 hectares, or acres or more in some places. Image courtesy of Lincoln Pratson, Duke University. Page 46 Share Cite Suggested Citation: Fractal geometry, the study of structures and patterns with non-integer dimensions, arose from an attempt to measure the length of the coastline of Britain.
Fractals and their relatives continue to facilitate our understanding of the spatial structure of landscapes. The emergence of complex systems and pattern formation as research areas in physics, mathematics, and other sciences has brought new attention to geopatterns from these communities.
Consider the evenly spaced valleys in locations as disparate as the humid Appalachian Mountains of Pennsylvania, the Coast Ranges of semiarid central California, and the steep flanks of arid Death Valley, southern California Figure 2.
Valley spacing is plotted against the length at which the time scales for specific types of erosion and stream incision are equal.
Stephen B DeLong, Ph.D.
This length scale is directly proportional to the valley spacing produced in a numerical model of landform evolution gray points, with linear trend highlighted blue and to the measured valley spacing at five field sites yellow points. Insets are shaded relief maps of sections of the sites, with vegetation filtered out of the laser altimetry data to show the underlying topography.
The georeferenced database is available at: DNA matrices and trees are avalaible at http: Abstract In the context of molecularly-dated phylogenies, inferences informed by ancestral habitat reconstruction can yield valuable insights into the origins of biomes, palaeoenvironments and landforms.
In this paper, we use dated phylogenies of 12 plant clades from the Cape Floristic Region CFR in southern Africa to test hypotheses of Neogene climatic and geomorphic evolution. Our combined dataset for the CFR strengthens and refines previous palaeoenvironmental reconstructions based on a sparse, mostly offshore fossil record.
Our reconstructions show remarkable consistency across all 12 clades with regard to both the types of environments identified as ancestral, and the timing of shifts to alternative conditions. They reveal that Early Miocene land surfaces of the CFR were wetter than at present and were dominated by quartzitic substrata. These conditions continue to characterize the higher-elevation settings of the Cape Fold Belt, where they have fostered the persistence of ancient fynbos lineages.
Although the Late Miocene may have seen some exposure of the underlying shale substrata, the present-day substrate diversity of the CFR lowlands was shaped by Pliocene-Pleistocene events. Particularly important was renewed erosion, following the post-African II uplift episode, and the reworking of sediments on the coastal platform as a consequence of marine transgressions and tectonic uplift. These changes facilitated adaptive radiations in some, but not all, lineages studied.
Introduction A robust knowledge of the palaeoenvironment underpins both our understanding of contemporary biodiversity [ 12 ] and our ability to manage and conserve biodiversity in the face of ongoing environmental change [ 3 ]. Invariably, however, palaeoenvironmental inference relies on palaeontological e. Insights gained from the fossil record, for example, are commonly fragmentary owing to spatiotemporal variability in taphonomic conditions [ 7 ].
In addition, many fossil deposits contain material sourced from extensive areas e. Abiotic proxies present challenges of their own. Some are difficult to interpret because they are controlled by multiple factors e.
Finally, it is not uncommon for different proxies to yield contrasting interpretations, exacerbating uncertainty of palaeoenvironmental reconstructions [ 11 ]. These challenges are exemplified in our palaeoenvironmental understanding of the Cape Floristic Region CFR; [ 12 ]an area renowned for its remarkable floristic richness and endemism. Although climatic and geological events during the Neogene are commonly invoked to explain the contemporary richness of the CFR flora [ 13 — 15 ], a lack of certainty about the extent and timing of these events hampers robust testing of these ideas.
For example, the development of the modern summer-arid climate of the CFR has frequently been linked to initiation of oceanic forcing by upwelling of the Benguela current 10—14 Ma [ 16 ], as inferred on the basis of isotopic evidence for Antarctic ice sheet expansion [ 10 ]. The records contained in the offshore deposition of sediment, nanofossils [ 1718 ] and marine illite, however, present a more complex picture of climatic shifts across the region.
These data imply a prevalence of arid conditions along the CFR west coast from Based on these patterns, it has recently been postulated that the modern seasonally-arid climate of the western CFR, and its associated flora, was only established well after the initiation of Benguela upwelling, perhaps as recently as 3—5 Ma [ 24 ].
Although the first appearance of arid-adapted elements in the fossil record offers a means to constrain the inferred origination time of the modern summer-arid climate of the western CFR, a severe dearth of Neogene fossil sites, particularly in the interior, is critically limiting.