DOCSLIB.ORG

The Tooth of Time: the North American Cordillera from Tanya Atwater to Karin Sigloch

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Tooth of Time: the North American Cordillera from Tanya Atwater to Karin Sigloch See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/270679894 The Tooth of Time: The North American Cordillera from Tanya Atwater to Karin Sigloch Article · September 2013 DOI: 10.12789/geocanj.2013.40.009 CITATION READS 1 527 1 author: Paul F. Hoffman University of Victoria 108 PUBLICATIONS 12,001 CITATIONS SEE PROFILE Some of the authors of this publication are also working on these related projects: Snowball Earth View project All content following this page was uploaded by Paul F. Hoffman on 04 April 2015. The user has requested enhancement of the downloaded file. GEOSCIENCE CANADA Volume 40 2013 71 COLUMN The Tooth of Time: batholith; R.V. Fisher and Bill Wise, Not long after, he became legendary the Cenozoic volcanic fields; and Pres for a different reason. As a Richfield The North American Cloud, the Death Valley area. Yet all Oil Corporation geologist, Natland Cordillera from Tanya the trips had one thing in common: proposed that detonating up to 100 Atwater to Karin Sigloch sooner or later, at every stop, the talk underground nuclear devices (atomic would turn to Tanya. Tanya says this bombs) might allow Athabasca Tar and Tanya says that. The trip leaders Sands oil to be extracted by conven- Paul F. Hoffman would get in a tizzy, like actors handed tional means. A pilot project outside 1216 Montrose Ave., Victoria, BC a new script at show time. If anyone Fort McMurray (Project Cauldron, V8T 2K4 was upset because Tanya was a woman later renamed Project Oilsand), backed in a man’s game, they didn’t say so, but by the government of Alberta, I remember the first time I met Tanya Atwater. She was still a graduate stu- a marine geophysicist interpreting the received federal government approval dent at Scripps Institution of complexities of onshore California following the Conservative landslide Oceanography, but over a year had geology was something else. For my under John Diefenbaker in 1958. passed since her paper came out on the part, I hadn’t the foggiest notion who When Lester Pearson’s Liberals were San Andreas Fault, arguably the best this Tanya person was, but I inferred elected in 1963, the project was quietly paper ever written on continental geol- that she must be a pretty formidable cancelled in line with Canada’s policy ogy (Atwater 1970). I was reminded of character. of nuclear non-proliferation. Four our meeting a few months ago, during Returning from one of the decades later, tar sands oil production a talk I heard at the Pacific Geoscience last trips of the year, we pulled off the would become a reality, not through Centre in Sidney, BC. coastal highway west of Ventura to nuclear technology but through $80-a- The plate tectonic revolution examine an upturned section of Upper barrel oil. was a great leveller: everyone found Pliocene turbidites. In the 1930’s, an Given what had followed— themselves in the same boat, regardless enterprising young micropaleontologist Kennedy’s assassination, Civil Rights, of age or experience. Yet, having come had compared Plio-Pleistocene Viet Nam, Richard Nixon—our from one dead orogenic belt, the cen- foraminifera in the subsurface of the thoughts were not about tar sand when tral Appalachians, to study another Ventura Basin with species living today we ran into another group of geolo- one, six times older, prudence urged off the California coast. He found that gists as we left the outcrop. Even then, me to see a living orogen first-hand. So the graded sandstone beds carry a Berkeley hippy with beads, long curly I eagerly accepted an offer—GSC reworked and indigenous shallow- hair and a flower-print dress, stood out granting leave-without-pay—to teach water, even lagoonal forms, while the in a group of geologists. She was about classes for 9 months at UCSB (Univer- shales have exclusively indigenous a year younger than I and was at least 7 sity of California – Santa Barbara), forams similar to those found today at months pregnant. When she talked, then a hotbed of igneous and Califor- water depths of 300–600 m (Natland effervesced would be a more apt nia geology. The geology department 1963). He had been ridiculed for sug- description, she giggled and flapped had been built up by Aaron Waters, gesting that the sandstones and associ- her hands. Before we parted, John who brought from Johns Hopkins the ated gravels were physically transported Crowell turned, beaming, and said, tradition of regular weekend field trips to deeper water, then thought to be the “Paul, meet Tanya Atwater”. for incoming graduate students. John reserve of strictly fine-grained Tanya grew up in Los Angeles, Crowell and Art Sylvester led trips to deposits, but after the turbidite revolu- where her mother was a botanist and the San Andreas Fault zone and the tion of 1950 (Kuenen and Migliorini her father an engineer. She loved Salton Sea; Cliff Hopson, the Coast 1950), Manley Natland became a leg- geometry in school and thought of Range ophiolites and the Sierra Nevada end in sedimentology (Walker 1973). becoming an artist until age 15, when Geoscience Canada, v. 40, http://dx.doi.org/10.12789/geocanj.2013.40.009 © 2013 GAC/AGC® 72 the launch of the Sputnik drew her during an upcoming cruise to the features had emerged. Tanya gravitated attention to science and engineering. Gorda Rift, north of the Mendocino to Menard’s group and soon found She went to MIT (Massachusetts Insti- Fracture Zone. He needed a capable that she and Menard shared a common tute of Technology), where women student to work up the data and he trait—the need to discuss geologic could enroll in those fields, and was in was willing to fight to have a woman structures with pencils on scraps of her fifth major in three years when she allowed on board the cruise. The high- paper (Atwater 2001). Menard was “accidentally took a physical geology course resolution survey showed that active troubled that the larger Pacific frac- [taught by petrologist W.H. Dennon] volcanism was limited to the axial rift tures zones have disturbed regions of and was hooked immediately” (Atwater valley and that the ridge crests were structural complexity, where their 2001). Field camp in Montana ban- not volcanic in origin but structural traces deviate from small circles in ished any doubts and, eager to return uplifts flanked by inward-dipping nor- seeming defiance of a cardinal rule of to California where “rocks don’t spend mal faults. The resulting report likely plate tectonics. However, the rule that most of their time covered by green or white satisfied her orals committee: it was transform faults follow small circles stuff”, she transferred to UC – Berkeley published as the lead article in Science with respect to the rotation pole in 1963, graduating two years later in (Atwater and Mudie 1968). between two plates is valid only if the geophysics. The hippy scene was in its The years 1967–68 were a rotation pole remains fixed. In a sys- early heyday. watershed. Tuzo Wilson’s concept of tem with multiple plates, competing in Back east again as a summer mobile rigid plates (Wilson 1965) had a struggle for existence, rotation poles intern in 1965, she saw Tuzo Wilson been given mathematical expression in must shift from time to time with con- demonstrate transform faults when it terms of Euler rotations on a sphere, sequent changes in sea-floor spreading was a new concept (Coode 1965; Wil- allowing the concept to be tested quan- direction. In a series of papers, the son 1965). The next year, working as a titatively (Bullard et al. 1965; McKenzie patriarch and the graduate student technician at the Geophysics Institute and Parker 1967; Morgan 1968; Le showed that the disturbed zones are in Santiago, Chile, she heard Jim Heirt- Pichon 1968; see also Le Pichon 1991; not random but are systematically relat- zler report on a new magnetic profile Frankel 2012a, b). Breaking ranks with ed to episodic changes in sea-floor obtained across the Pacific–Antarctic their elders, three young seismologists spreading direction (Menard and Atwa- Rise (Pitman and Heirtzler 1966). The assembled comprehensive independent ter 1968, 1969; Atwater and Menard Eltanin-19 profile remains the longest, support for plate tectonics (Isacks, 1970). They inferred that a particularly cleanest and most symmetrical of any Oliver and Sykes 1968)—rescuing seis- marked change in spreading direction spreading ridge in the world (Atwater mology from ignominy for had occurred ~55 Ma, according to the 2001), convincing even Lamont- stonewalling mantle convection and Heirtzler time scale (Heirtzler et al. Doherty’s Director Maurice Ewing and continental drift. Perhaps most impor- 1968), close to the age of the subse- other skeptics that sea-floor spreading tant, magnetic profiles covering large quently described bend in the Hawaii- was a reality (Glen 1982; Le Pichon parts of the Pacific, South Atlantic and Emperor seamount chain. From 1986). Like its continuation, the East Indian oceans, which Lamont-Doherty Menard, Tanya also learned that any Pacific Rise, it had been thought a vessels for years had been systematical- new concept, to gain attention, needs a poor candidate for sea-floor spreading ly acquiring for no apparent reason, name that clicks (Atwater 2001). Soon, because it lacked an axial rift valley. were compiled and interpreted in everyone was talking about “leaky” Historians mark 1967 as the terms of sea-floor spreading (Dickson transform faults (Menard and Atwater year the plate tectonics revolution et al. 1968; Le Pichon and Heirtzler 1969). ended, but for marine geophysicists it 1968; Pitman et al.
Load more

Recommended publications
  • Two Contrasting Phanerozoic Orogenic Systems Revealed by Hafnium Isotope Data William J
    ARTICLES PUBLISHED ONLINE: 17 APRIL 2011 | DOI: 10.1038/NGEO1127 Two contrasting Phanerozoic orogenic systems revealed by hafnium isotope data William J. Collins1*(, Elena A. Belousova2, Anthony I. S. Kemp1 and J. Brendan Murphy3 Two fundamentally different orogenic systems have existed on Earth throughout the Phanerozoic. Circum-Pacific accretionary orogens are the external orogenic system formed around the Pacific rim, where oceanic lithosphere semicontinuously subducts beneath continental lithosphere. In contrast, the internal orogenic system is found in Europe and Asia as the collage of collisional mountain belts, formed during the collision between continental crustal fragments. External orogenic systems form at the boundary of large underlying mantle convection cells, whereas internal orogens form within one supercell. Here we present a compilation of hafnium isotope data from zircon minerals collected from orogens worldwide. We find that the range of hafnium isotope signatures for the external orogenic system narrows and trends towards more radiogenic compositions since 550 Myr ago. By contrast, the range of signatures from the internal orogenic system broadens since 550 Myr ago. We suggest that for the external system, the lower crust and lithospheric mantle beneath the overriding continent is removed during subduction and replaced by newly formed crust, which generates the radiogenic hafnium signature when remelted. For the internal orogenic system, the lower crust and lithospheric mantle is instead eventually replaced by more continental lithosphere from a collided continental fragment. Our suggested model provides a simple basis for unravelling the global geodynamic evolution of the ancient Earth. resent-day orogens of contrasting character can be reduced to which probably began by the Early Ordovician12, and the Early two types on Earth, dominantly accretionary or dominantly Paleozoic accretionary orogens in the easternmost Altaids of Pcollisional, because only the latter are associated with Wilson Asia13.
    [Show full text]
  • Climate Change May Induce Connectivity Loss and Mountaintop Extinction in Central American Forests ✉ Lukas Baumbach 1 , Dan L
    ARTICLE https://doi.org/10.1038/s42003-021-02359-9 OPEN Climate change may induce connectivity loss and mountaintop extinction in Central American forests ✉ Lukas Baumbach 1 , Dan L. Warren 2, Rasoul Yousefpour1 & Marc Hanewinkel 1 The tropical forests of Central America serve a pivotal role as biodiversity hotspots and provide ecosystem services securing human livelihood. However, climate change is expected to affect the species composition of forest ecosystems, lead to forest type transitions and trigger irrecoverable losses of habitat and biodiversity. Here, we investigate potential impacts of climate change on the environmental suitability of main plant functional types (PFTs) across Central America. Using a large database of occurrence records and physiological data, 1234567890():,; we classify tree species into trait-based groups and project their suitability under three representative concentration pathways (RCPs 2.6, 4.5 and 8.5) with an ensemble of state-of- the-art correlative modelling methods. Our results forecast transitions from wet towards generalist or dry forest PFTs for large parts of the study region. Moreover, suitable area for wet-adapted PFTs is projected to latitudinally diverge and lose connectivity, while expected upslope shifts of montane species point to high risks of mountaintop extinction. These findings underline the urgent need to safeguard the connectivity of habitats through biological corridors and extend protected areas in the identified transition hotspots. 1 Chair of Forestry Economics and Forest Planning,
    [Show full text]
  • (1987): "Tectonomagmatic Evolution of Cenozoic Extension in the North American Cordillera"
    Downloaded from http://sp.lyellcollection.org/ by Frances J Cooper on January 21, 2013 Geological Society, London, Special Publications Tectonomagmatic evolution of Cenozoic extension in the North American Cordillera Brian P. Wernicke, Philip C. England, Leslie J. Sonder and Robert L. Christiansen Geological Society, London, Special Publications 1987, v.28; p203-221. doi: 10.1144/GSL.SP.1987.028.01.15 Email alerting click here to receive free e-mail alerts when service new articles cite this article Permission click here to seek permission to re-use all or request part of this article Subscribe click here to subscribe to Geological Society, London, Special Publications or the Lyell Collection Notes © The Geological Society of London 2013 Downloaded from http://sp.lyellcollection.org/ by Frances J Cooper on January 21, 2013 Tectonomagmatic evolution of Cenozoic extension in the North American Cordillera B.P. Wernicke, R.L. Christiansen, P.C. England & L.J. Sonder SUMMARY: The spatial and temporal distributions of Cenozoic extension and magmatism in the Cordillera suggest that the onset of major crustal extension at a particular latitude was confined to a relatively narrow belt (< 100 km, pre-extension) and followed the onset of intermediate and silicic magmatism by no more than a few million years. Extension began in early Eocene time in southern British Columbia, northern Washington, Idaho and Montana. Farther S, extension began at about the Eocene- Oligocene boundary in the Great Basin and slightly later in the Mojave-Sonora Desert region. The intervening area, at the latitude of Las Vegas, remained quiescent until mid- Miocene time. Compositional and isotopic characteristics of most pre-Miocene magmas are consistent with their containing major components of melted continental crust.
    [Show full text]
  • Brief Overview of North American Cordilleran Geology by Cin-Ty Lee Topography Map of North America
    Brief overview of North American Cordilleran geology by Cin‐Ty Lee Note: make sure to take notes as I will talk or sketch on the board many things that are not presented explicitly in these slides Topography map of North America Topography map How does the NthNorth AiAmerican Cor dillera fit itinto a glbllobal contt?text? Dickinson 2004 P‐wave tomography: Seismic structure beneath western USA Burdick et al. 2008 Crustal provinces of North America (Laurentia) ‐Proterozoic and Archean terranes were already assembled by 1.6 Ga Hoffman, 1988 Crustal provinces in southwestern USA Hoffman, 1988 Bennett and DePaolo, 1987 Some examples of tectonic margins for your reference Dickinson and Snyder, 1978 1.1 Ga = Rodinia Super‐continent (Grenvillian age) Neo‐Proterozoic = Rodinia breaks up “western” margin of Laurentia represents a passive margin due to opening of the Panthalassan ocean 700‐400 Ma Western margin of Laurentia represents a passive margin Dickinson and Snyder, 1978 400‐250 Ma Passive margin is interrupted in Devonian times by the accretion of island arcs Antler and Sonoma orogenies Accretion of allochthonous terranes to the western margin of the NhNorth AiAmerican craton Antler/Sonoma orogenies result in the accretion of Paleozoic island arc terranes to western North America Permian Formation of Pangea “”“western” margin of NhNorth AiAmerica now didominate d by subduct ion zone 250‐50 Ma Subduction results in continued accretion of fringing island arcs and the generation of continental magmatic arcs Sierra Nevada batholith Sevier and
    [Show full text]
  • The American Cordillera: a Long Journey Through Time & Space
    The American Cordillera: A Long Journey Through Time & Space Part III:The North American Taphrogen Lecture 25: April 25, G. Zandt An overview of the collapse of the American Cordillera 1 Some of the Big Questions • What caused the extreme inboard migration of deformation and magmatism during the Laramide? [Flat Slab] • What caused the mid-Tertiary extensional collapse and ignimbrite flareup? [Slab Rollback] • Why is the extension and associated magmatisn separated into two domains with different spatial-temporal evolutions? • How did the Colorado Plateau escape significant deformation and magmatism during both periods? Major questions we want to address today. 2 North American Cordillera Topography is the first-order expression of orogeny, and high topography extends half way across the continent (>1000 km). And it remains high despite significant extension which normally leads to subsidence. 3 Western US today We will follow Dickinson (2002) in this review of the Cordilleran taphrogen. He follows Sengor in dividing the Basin and Range taphrogen into the Numic and Piman subtaphrogens. Black bodies are core complexes with arrows indicating direction of vergence (movement of upper plate). We will focus today on the relationship between the subtaphrogens and the Colorado Plateau–Laramide Rocky Mountains. Dickinson, W. R., The Basin and Range Province as a Composite Extensional Domain, Int. Geol. Rev., 44, 1-38, 2002. 4 The tectonic evolution of the Cordillera can be divided into 7 frames (Coney): 1) Formation of the continental margin in late Precambrian time and development of the Cordilleran passive margin. 2) Mid- to late Paleozoic brief orogenic events (Antler, Ancestral Rockies, Sonoma orogenies).
    [Show full text]
  • Climate Change in Central America and Mexico: Regional Climate Model Validation and Climate Change Projections
    Clim Dyn DOI 10.1007/s00382-011-1099-9 Climate change in Central America and Mexico: regional climate model validation and climate change projections Ambarish V. Karmalkar • Raymond S. Bradley • Henry F. Diaz Received: 6 January 2010 / Accepted: 10 May 2011 Ó Springer-Verlag 2011 Abstract Central America has high biodiversity, it har- the form of orographic precipitation show significant bors high-value ecosystems and it’s important to provide decreases in precipitation in the dry season. Projected cli- regional climate change information to assist in adaptation matic changes can have detrimental impacts on biodiver- and mitigation work in the region. Here we study climate sity as they are spatially similar, but far greater in change projections for Central America and Mexico using magnitude, than those observed during the El Nin˜o events a regional climate model. The model evaluation shows its in recent decades that adversely affected species in the success in simulating spatial and temporal variability of region. temperature and precipitation and also in capturing regio- nal climate features such as the bimodal annual cycle of keywords Regional climate change Á Biodiversity Á precipitation and the Caribbean low-level jet. A variety of Central America climate regimes within the model domain are also better identified in the regional model simulation due to improved resolution of topographic features. Although, the model 1 Introduction suffers from large precipitation biases, it shows improve- ments over the coarse-resolution driving model in simu- The Mexican and Central American landmass has consid- lating precipitation amounts. The model shows a dry bias erable topographic relief, which implies the existence of in the wet season and a wet bias in the dry season sug- large gradients in many critical climate variables such as gesting that it’s unable to capture the full range of pre- temperature, precipitation, humidity, and wind.
    [Show full text]
  • Cross Cordillera Field Trip Guide
    GS Field Trip: End of Summer 2016 GS191/291 (Miller, no Klemperer (went to Tibet), Lund Snee, Gottlieb) Listed as Fall Quarter class under Miller Crossing the Cordillera: From the Colorado Plateau to the Sierra Nevada Field trip (1 credit), advanced ugrad to grad level, but all welcome Dates: September 15 to Sept. 21 (T.A. Eric Gottlieb) There is unprecedented controversy about the paleo-topographic evolution of the western United States. How thick and how high was the crust following Mesozoic crustal shortening? Did the region between the Sierra Nevada and the Colorado Plateau form a high plateau, the Nevadaplano, underlain by 60 km thick crust? When did this thick crust collapse to its present crustal thickness of only 30 km? Did extension happen as a result of, during and shortly after crustal thickening? Or did extension take place only in the Miocene, during formation of Basin and Range topography? How much stretching is represented by Basin and Range faulting? Can it account for thinning of crust by 30 km? This field trip will provide you with an exceptional opportunity to view a complete cross-section of the geology of the southern part of the North American Cordillera, from the undeformed Colorado Plateau on the east to Mount Whitney and the Mesozoic Sierra Nevada arc on the west. With these big questions in mind, our stops will focus on Mesozoic shortening, when the Cordillera is believed to have looked like the Andes, and on younger extensional structures (including a variety faults in Death Valley), with a critical view and discussion of age, geometry and offset along normal faults.
    [Show full text]
  • Climatic Changes in Mountain Regions of the American Cordillera and the Tropics: Historical Changes and Future Outlook
    Arctic, Antarctic, and Alpine Research, Vol. 46, No. 4, 2014, pp. 1-9 Climatic changes in mountain regions of the American Cordillera and the tropics: historical changes and future outlook Henry F. Diaz* Abstract Raymond S. Bradley† and We review some recent work regarding climatic changes in selected mountain Liang Ning† regions, with particular attention to the tropics and the American Cordillera. Key aspects of climatic variability and trends in these regions are the amplification *Corresponding author: NOAA/Cooperative of surface warming trends with height, and the strong modulation of tempera- Institute for Research in Environmental Sciences, ture trends by tropical sea surface temperature, largely controlled by changes University of Colorado, 325 Broadway, Boulder, Colorado 80305, U.S.A., in El Niño–Southern Oscillation on multiple time scales. Corollary aspects of henry.f.diaz@noaa.gov these climate trends include the increase in a critical plant growth temperature †Department of Geosciences, University of threshold, a rise in the freezing level surface, and the possibility of enhanced Massachusetts, 611 North Pleasant Street, subtropical drying. Anthropogenic global warming projections indicate a strong Amherst, Massachusetts 01003, U.S.A. likelihood for enhancement of these observed changes. DOI: http://dx.doi.org/10.1657/1938-4246-46.4.1 Introduction potential changes in future climate, as indicated by regional atmospheric circulation models. We update some previous Mountain regions cover about one-fifth of the earth’s latitudinal-altitudinal transects with more recent observations and continental areas, providing basic life support directly for close to climate model simulations (Diaz et al., 2003b, 2011; Bradley et al., 10% of the world’s population, and indirectly to over half.
    [Show full text]
  • Modeling Potential Equilibrium States of Vegetation and Terrestrial Water
    Modeling Potential Equilibrium States of Vegetation and Terrestrial Water Cycle of Mesoamerica under Climate Change Scenarios Pablo Imbach, Luis Molina, Bruno Locatelli, Olivier Roupsard, Gil Mahe, Ronald Neilson, Lenin Corrales, Marko Scholze, Philippe Ciais To cite this version: Pablo Imbach, Luis Molina, Bruno Locatelli, Olivier Roupsard, Gil Mahe, et al.. Modeling Potential Equilibrium States of Vegetation and Terrestrial Water Cycle of Mesoamerica under Climate Change Scenarios. Journal of Hydrometeorology, American Meteorological Society, 2012, 13, pp.665-680. 10.1175/JHM-D-11-023.1. cirad-00701344 HAL Id: cirad-00701344 http://hal.cirad.fr/cirad-00701344 Submitted on 25 Aug 2012 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. APRIL 2012 IMBACHETAL. 665 Modeling Potential Equilibrium States of Vegetation and Terrestrial Water Cycle of Mesoamerica under Climate Change Scenarios* 1 1 # 1,@ & PABLO IMBACH, LUIS MOLINA, BRUNO LOCATELLI, OLIVIER ROUPSARD, GIL MAHE´ , ,&& 11 ## @@ RONALD NEILSON,** LENIN CORRALES, MARKO SCHOLZE, AND PHILIPPE CIAIS
    [Show full text]
  • Documenting Hydroclimate Variability in the American Cordillera
    Mountain “Water Towers” and Global Change- documenting hydroclimate variability in the American Cordillera B. H. Luckman Department of Geography, University of Western Ontario, LONDON, Ontario, Canada N6A 5C2. Luckman@uwo.ca Abstract In many parts of the western Americas cordilleran runoff is the primary source of water for adjacent semi-arid lowlands. Climate and land use changes are resulting in changes in the amount, seasonality and variability of streamflow, which, combined with increasing demand, creates significant problems for contemporary and future water management. This session focuses on past, present and future changes in hydrologic variability with examples from the mountain areas of the USA, Mexico, Bolivia, Chile and Argentina. It examines the contribution of glaciers, snowmelt and anthropogenic activities to these changes; discusses the causes, nature and range of variability at centennial-annual timescales; illustrates the impacts of these changes on society and explores the implications of these changes for future water management in the adjacent lowlands. Critically, these studies demonstrate the nature and range of hydroclimatic variability that must be accommodated in meeting sustainable future water management needs in these regions. Introduction In many parts of the western Americas cordilleran runoff is the primary source of water for adjacent semi-arid lowlands. This illustrates the concept that mountain areas function as “Water Towers” (Liniger et al., 1998, Messerli et al., 2004), storing and then releasing water to the surrounding areas. Ongoing climate and land use changes are resulting in changes in the amount, seasonality and variability of streamflow, which, combined with increasing demand, creates significant problems for contemporary and future water management.
    [Show full text]
  • Impacts of Climate Change on Ecosystem Hydrological Services of Central America Water Availability
    6163 T&F Climate Change Impacts on tropical forests:Layout 1 18/3/15 5:19 pm Page 65 3 Impacts of climate change on ecosystem hydrological services of Central America Water availability Pablo Imbach, Bruno Locatelli, Juan Carlos Zamora, Emily Fung, Lluis Calderer, Luis Molina and Philippe Ciais Introduction Climate change and land use change are predicted to be the two main drivers of global biodiversity alterations (Sala et al. 2000). The effects of climate change on biodiversity are manifested at different scales, from genes (i.e. generating mut- ations and simplifying gene pools) to species (i.e. extinctions and range modifications) and ecosystems (i.e. community composition and distribution changes). These effects influence ecosystem functions and processes, for instance changes in the abundance and composition of plant species may influence water cycle, nutrient and carbon dynamics, trophic interactions and disturbance regimes (Chapin III et al. 1997; Diaz et al. 2004). Ecosystem functions are linked to the provision of ecosystem goods and services when human values are considered (de Groot et al. 2002; MEA 2005). Many authors have highlighted the value of these ecosystem services for sustainable development, globally (Costanza et al. 1997) or locally (Lutz et al. 2000; Woodward and Wui 2001; Pattanayak 2004). Terrestrial ecosystems provide an array of watershed services, for instance the regulation of hydrological flows, benefiting agriculture, drinking water users, energy production, or transportation (Costanza et al. 1997; MEA 2005). Watershed services are of outmost importance in many developing countries where water is a crucial development issue, such as Central America (Locatelli et al.
    [Show full text]
  • Dickinson2004.Pdf
    7 Apr 2004 20:19 AR AR211-EA32-02.tex AR211-EA32-02.sgm LaTeX2e(2002/01/18) P1: GCE 10.1146/annurev.earth.32.101802.120257 Annu. Rev. Earth Planet. Sci. 2004. 32:13–45 doi: 10.1146/annurev.earth.32.101802.120257 Copyright c 2004 by Annual Reviews. All rights reserved First published online as a Review in Advance on November 10, 2003 EVOLUTION OF THE NORTH AMERICAN CORDILLERA William R. Dickinson Department of Geosciences, University of Arizona, Tucson, Arizona 85721; email: wrdickin@geo.arizona.edu Key Words continental margin, crustal genesis, geologic history, orogen, tectonics ■ Abstract The Cordilleran orogen of western North America is a segment of the Circum-Pacific orogenic belt where subduction of oceanic lithosphere has been under- way along a great circle of the globe since breakup of the supercontinent Pangea began in Triassic time. Early stages of Cordilleran evolution involved Neoproterozoic rifting of the supercontinent Rodinia to trigger miogeoclinal sedimentation along a passive continental margin until Late Devonian time, and overthrusting of oceanic allochthons across the miogeoclinal belt from Late Devonian to Early Triassic time. Subsequent evolution of the Cordilleran arc-trench system was punctuated by tectonic accretion of intraoceanic island arcs that further expanded the Cordilleran continental margin during mid-Mesozoic time, and later produced a Cretaceous batholith belt along the Cordilleran trend. Cenozoic interaction with intra-Pacific seafloor spreading systems fostered transform faulting along the Cordilleran continental margin and promoted incipient rupture of continental crust within the adjacent continental block. INTRODUCTION Geologic analysis of the Cordilleran orogen, forming the western mountain system of North America, raises the following questions: 1.
    [Show full text]