Pub Date : 2021-10-26DOI: 10.1080/02723646.2021.1990506
K. C. Glover, J. George, L. Heusser, G. MacDonald
ABSTRACT We compiled pollen sequences from lake and offshore cores at least 6,000 years old (6 ka) for the Mediterranean and Marine ecoregions of the US West Coast. Principal Component Analysis highlighted vegetation differences in core-tops, the Holocene Thermal Maximum (6 ka) and Last Glacial Maximum (LGM, 19 ka). Core-top and HTM ordination produced clusters that reflected geographic clusters in the Sierra Nevada, and the Pacific Northwest coast. Little change in these clusters between 6-0 ka suggested that vegetation communities in coastal and alpine settings persisted, despite warmer global temperatures. PCA outliers reflect distinct pollen assemblages that often were isolated sites or bordered the Great Basin. During the LGM, greater shrub and herb presence in the Marine ecoregion interior indicated enhanced aridity, while conifer presence in coastal and Southern California indicated moist conditions. Qualitatively, tree taxa from the Last Interglacial (~130–120 ka) showed how vegetation shifted over 6–10 kyr from alder, to oak, then redwood, a successional pattern that began again at the Late Glacial (~15 ka). In future West Coast pollen studies, sampling and chronologic control at centennial resolution will enable further study of more time periods and rates of vegetation change in response to climate.
{"title":"West Coast vegetation shifts as a response to climate change over the past 130,000 years: geographic patterns and process from pollen data","authors":"K. C. Glover, J. George, L. Heusser, G. MacDonald","doi":"10.1080/02723646.2021.1990506","DOIUrl":"https://doi.org/10.1080/02723646.2021.1990506","url":null,"abstract":"ABSTRACT We compiled pollen sequences from lake and offshore cores at least 6,000 years old (6 ka) for the Mediterranean and Marine ecoregions of the US West Coast. Principal Component Analysis highlighted vegetation differences in core-tops, the Holocene Thermal Maximum (6 ka) and Last Glacial Maximum (LGM, 19 ka). Core-top and HTM ordination produced clusters that reflected geographic clusters in the Sierra Nevada, and the Pacific Northwest coast. Little change in these clusters between 6-0 ka suggested that vegetation communities in coastal and alpine settings persisted, despite warmer global temperatures. PCA outliers reflect distinct pollen assemblages that often were isolated sites or bordered the Great Basin. During the LGM, greater shrub and herb presence in the Marine ecoregion interior indicated enhanced aridity, while conifer presence in coastal and Southern California indicated moist conditions. Qualitatively, tree taxa from the Last Interglacial (~130–120 ka) showed how vegetation shifted over 6–10 kyr from alder, to oak, then redwood, a successional pattern that began again at the Late Glacial (~15 ka). In future West Coast pollen studies, sampling and chronologic control at centennial resolution will enable further study of more time periods and rates of vegetation change in response to climate.","PeriodicalId":54618,"journal":{"name":"Physical Geography","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2021-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47132503","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-10-21DOI: 10.1080/02723646.2021.1993770
A. Bashir, M. Gül, Ceren Küçükuysal, Göksu Uslular
ABSTRACT This study investigates the spectacular geomorphological features of Jurassic (Younger) Granites in NE Nigeria by using field observations and some structural (i.e. joints) analyses. The study area is in the Sahel region of the Subsaharan of Africa as a transition zone between the Sahara Desert and Equatorial region, where many studies have focused on the loess deposits, ergs, climate change, and Saharan Desert boundary changes. Morphological features of rocks in the study area have not been widely discussed in the literature. However, inselbergs, ruwares, and pillar structures are the major landforms in this vast plain with an arid environment. Boulders, blocks, mushrooms, and corestones, tafoni, shelter caves, flared slopes, polygonal cracks, and weathering pits are minor features. Weathering products consisting of white-colored, granular quartz-bearing grus and red clayey laterite surround the granite masses. Subsurface weathering has favored the formation of major geomorphological features; however, subsequent superficial weathering leading to hydration and stripping occurred mostly under the humid climatic conditions with seasonal variation of dry and humid climatic conditions. Local paleoenvironmental – paleoclimatic conditions would have prevented excess weathering and erosion in the study area.
{"title":"Geomorphological features of the Jurassic Granites in NE Nigeria (Southern Sahara)","authors":"A. Bashir, M. Gül, Ceren Küçükuysal, Göksu Uslular","doi":"10.1080/02723646.2021.1993770","DOIUrl":"https://doi.org/10.1080/02723646.2021.1993770","url":null,"abstract":"ABSTRACT This study investigates the spectacular geomorphological features of Jurassic (Younger) Granites in NE Nigeria by using field observations and some structural (i.e. joints) analyses. The study area is in the Sahel region of the Subsaharan of Africa as a transition zone between the Sahara Desert and Equatorial region, where many studies have focused on the loess deposits, ergs, climate change, and Saharan Desert boundary changes. Morphological features of rocks in the study area have not been widely discussed in the literature. However, inselbergs, ruwares, and pillar structures are the major landforms in this vast plain with an arid environment. Boulders, blocks, mushrooms, and corestones, tafoni, shelter caves, flared slopes, polygonal cracks, and weathering pits are minor features. Weathering products consisting of white-colored, granular quartz-bearing grus and red clayey laterite surround the granite masses. Subsurface weathering has favored the formation of major geomorphological features; however, subsequent superficial weathering leading to hydration and stripping occurred mostly under the humid climatic conditions with seasonal variation of dry and humid climatic conditions. Local paleoenvironmental – paleoclimatic conditions would have prevented excess weathering and erosion in the study area.","PeriodicalId":54618,"journal":{"name":"Physical Geography","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2021-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47199129","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-09-25DOI: 10.1080/02723646.2021.1978372
Alejandro César Valdés Carrera, M. Mendoza, Teodoro Carlón Allende, J. L. Macías
ABSTRACT Over the last few decades, the impact of landslides has increased in Latin America. However, there is a deficiency in the region of diagnostic studies on landslide hazards. This review analyzes the state of the art of studies on landslide hazard occurred in Latin America. A search for articles published from 2000 to 2019 was carried out in Scopus, WoS, SciELO, REDIB, and Redalyc. The search yielded 1,365 publications, which were purged obtaining 283 articles, analyzed through a database organized in four categories: general information, study area, research objectives, and methodology. We identified an increase in the number of publications from the year 2011. Seventy-five percent of the 20 countries in the region published papers on landslides that had occurred in these countries, mainly research focus on susceptibility and characterization, and a reduced number, on hazardousness, inventories, trigger factors and conditioning factors. The results suggest the opportunity to incorporate novel methods, tools, techniques, and inputs into research of landslides in Latin America. This review constitutes an analytical and critical contribution to the study of landslide hazards in the region and indicates the studies that are urgent to enforce its integral management in the region and in other intertropical zones.
{"title":"A review of recent studies on landslide hazard in Latin America","authors":"Alejandro César Valdés Carrera, M. Mendoza, Teodoro Carlón Allende, J. L. Macías","doi":"10.1080/02723646.2021.1978372","DOIUrl":"https://doi.org/10.1080/02723646.2021.1978372","url":null,"abstract":"ABSTRACT Over the last few decades, the impact of landslides has increased in Latin America. However, there is a deficiency in the region of diagnostic studies on landslide hazards. This review analyzes the state of the art of studies on landslide hazard occurred in Latin America. A search for articles published from 2000 to 2019 was carried out in Scopus, WoS, SciELO, REDIB, and Redalyc. The search yielded 1,365 publications, which were purged obtaining 283 articles, analyzed through a database organized in four categories: general information, study area, research objectives, and methodology. We identified an increase in the number of publications from the year 2011. Seventy-five percent of the 20 countries in the region published papers on landslides that had occurred in these countries, mainly research focus on susceptibility and characterization, and a reduced number, on hazardousness, inventories, trigger factors and conditioning factors. The results suggest the opportunity to incorporate novel methods, tools, techniques, and inputs into research of landslides in Latin America. This review constitutes an analytical and critical contribution to the study of landslide hazards in the region and indicates the studies that are urgent to enforce its integral management in the region and in other intertropical zones.","PeriodicalId":54618,"journal":{"name":"Physical Geography","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2021-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45312095","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Climate change and the carbon cycle","authors":"J. Holden","doi":"10.4324/9781003124405-4","DOIUrl":"https://doi.org/10.4324/9781003124405-4","url":null,"abstract":"","PeriodicalId":54618,"journal":{"name":"Physical Geography","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2021-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46985948","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
ABSTRACT The Kanchi, an eastward flowing river, traverses through the Ranchi plateau of the Proterozoic Chhotanagpur granite gneissic complex to meet its trunk stream, the Subarnarekha River. The present study analyzed longitudinal profiles and associated geomorphic indices of the Kanchi River and its tributaries to identify spatial variation in profile form and fluvial response to prevailing controls. This work was carried out using a digital dataset and maps, which were processed in a GIS environment to obtain longitudinal profiles, and different data required in best-fit modelling and geomorphic investigation of longitudinal profiles. The analyses indicate that the rivers are in dynamic equilibrium condition. Spatial distribution of geomorphic indices values reveals that longitudinal profile forms vary from one segment to another along river channels, and these irregularities in the form of prominent and minor knickpoints are highly concentrated in middle river basin areas. The absence of lithological variation and active tectonics, and close association of anomalously steep river segments with structural lineaments and landforms demonstrates structural control on river channel development. PCA denotes strong similarities between geomorphic indices. This understanding of longitudinal variation in river nature may help to formulate strategies for the sustainable development and management of river related resources.
{"title":"Geomorphic assessment of longitudinal profile of the Kanchi river basin, India: Recognition of dynamic equilibrium condition","authors":"Monali Banerjee, Debasish Ghosh, Subhadip Pal, Manas Karmakar","doi":"10.1080/02723646.2021.1978139","DOIUrl":"https://doi.org/10.1080/02723646.2021.1978139","url":null,"abstract":"ABSTRACT The Kanchi, an eastward flowing river, traverses through the Ranchi plateau of the Proterozoic Chhotanagpur granite gneissic complex to meet its trunk stream, the Subarnarekha River. The present study analyzed longitudinal profiles and associated geomorphic indices of the Kanchi River and its tributaries to identify spatial variation in profile form and fluvial response to prevailing controls. This work was carried out using a digital dataset and maps, which were processed in a GIS environment to obtain longitudinal profiles, and different data required in best-fit modelling and geomorphic investigation of longitudinal profiles. The analyses indicate that the rivers are in dynamic equilibrium condition. Spatial distribution of geomorphic indices values reveals that longitudinal profile forms vary from one segment to another along river channels, and these irregularities in the form of prominent and minor knickpoints are highly concentrated in middle river basin areas. The absence of lithological variation and active tectonics, and close association of anomalously steep river segments with structural lineaments and landforms demonstrates structural control on river channel development. PCA denotes strong similarities between geomorphic indices. This understanding of longitudinal variation in river nature may help to formulate strategies for the sustainable development and management of river related resources.","PeriodicalId":54618,"journal":{"name":"Physical Geography","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2021-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44904232","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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