Land Surface Stability Research Articles

Formation of desert pavements and the interpretation of lithic-strewn landscapes of the central Sahara

This study focuses on two different but interlinked lines of evidence that critically examine land surface processes contributing to the formation of desert pavements in the central Sahara. (1) Soil pedostratigraphies from the Messak plateau (SW Libya) illustrate phases of land surface stability and instability that reflect humid and arid phases of Quaternary climate, respectively. (2) The density and morphologies of surface lithic scatters in the same region were re-examined, based on data previously published by Foley and Lahr (2015, PLoS ONE). This re-examination shows that many surface clasts previously interpreted as lithics are better interpreted as formed by in situ weathering and wind abrasion. Furthermore, weathering, abrasion and deflation are the major processes by which desert clasts are formed and concentrated on the land surface, not human agency. Erosional Quaternary periods allowed for the formation of condensed pedostratigraphies by which surface clasts and lithics were mixed and concentrated on the land surface. These two independent lines of evidence show that desert land surfaces do not reflect a single time period of formation, and that Quaternary desert pavements (including any lithics located thereon) evolved in response to subaerial weathering and erosion processes.

Anthropogenic influence on rates of aeolian dune activity within the northern European Sand Belt and socio-economic feedbacks over the last ~2500 years

In North-Western Europe, Pleistocene sand sheets have been reactivated during phases of Holocene deforestation and agricultural land use. Although there are temporal overlaps between anthropogenic activity and sand sheet reactivation, the root cause and subsequent feedbacks between aeolian activity and societal response remain largely unknown. Here, we seek to establish cause and effect by examining the detailed co-variation in both timing and magnitude of aeolian and anthropogenic activity through the quantification of Holocene dune sediments in combination with archaeological and pollen records. These records indicate a series of complex phases of aeolian activity followed by landscape stabilization, which we attribute primarily to changing patterns of human impact. We find that a steady increase in dune deposition rates in the Medieval Period corresponds to an increase in settlement activity and deforestation (~AD 1000–1500). At their peak, Medieval deposition rates were 3.4 times larger than during the late Pleistocene, the period experiencing the most favourable natural conditions for aeolian sediment transport. Prior to the Medieval Period, relative land-surface stability (represented by a depositional hiatus) persisted from the late Pleistocene until the Roman Iron Age Period (AD 0–400). Deforestation to fuel iron production had minor impact on aeolian activity, as indicated by the lowest recorded deposition rate (0.12 ± 0.02 t/ha/a). Following the Medieval Period peak in deposition rates, aeolian activity diminished rapidly and coincided with the abandonment of nearby human settlement. This sequence of events provides evidence of a direct positive feedback in which Medieval agricultural overexploitation favoured aeolian activity that rendered the landscape practically unworkable for cropping agriculture. Based on our findings and a comprehensive review of Northern European sand belt activity, we interpret a very high sensitivity of aeolian activity to past and present human impact and argue that unsustainable land-use practices have been the cause for widespread settlement abandonment.

Atmospheric K-feldspar as a potential climate modulating agent through geologic time

Abstract Clouds and aerosols have a large, yet highly uncertain, effect on changes in Earth’s climate. A factor of particular note is the role played by ice-nucleating particles, which remains poorly understood. The mineral K-feldspar (Kfs) has recently been shown by a number of independent studies to nucleate ice in mixed-phase cloud conditions far more efficiently than other common minerals. Here, global atmospheric Kfs flux through geologic time is estimated; constrained by records of secular continental crust and biosphere evolution, plate tectonics, volcanism, glaciation, and attendant trends in land surface stability. The analysis reveals that Kfs flux today is at neither extreme of the range estimated across geological time. The present-day Kfs flux, however, is likely to be among the most spatially and temporally variable due to land surface change. The concept of an ice-nucleation efficiency factor that can be calculated from rocks, and also eolian sediments and soils, is proposed. This allows the impact of paleo-atmospheric dust to be estimated through the rock record alongside meteorological and atmospheric composition considerations. With the reasonable assumption that the ice-nucleating properties of Kfs are themselves independent of the background climate state, a better understanding of Kfs flux across a range of spatial and temporal scales will advance understanding of climate processes and interactions.

Micromorphological investigations of the Late Quaternary loess–paleosol sequences of the Kashmir Valley, India

The loess–paleosol sequences of the Karewa Group preserve a valuable repository of the Late Quaternary climatic changes and the landscape evolution history of the Karewa Basin of Kashmir Valley in their lithological and pedogenic records. Three representative loess–paleosol sections at Shankerpora (SP), Khan Sahib (KS) and Pattan (PT) localities were chosen for detailed lithostratigraphic fieldwork and micromorphological observations of thin sections. Lithostratigraphic analysis revealed lateral and vertical variation in thickness and number of paleosol profiles from south-west to north-west of the Karewa Basin suggesting the availability of land-surface for periodic loess deposition. The SP section is marked by 6 (SP-S6, S7, S8, S9, S10, S12), KS section by 3 (KS-S2, S4, S5) and PT section by 2 (PT-S1, S3) thick mature paleosol profiles. Theses paleosols have well developed ‘Ah’ and ‘Btk’ horizons representing prolonged land-surface stability when pedogenic processes outpace loess deposition. On the other hand comparatively thin to thick paleosol profiles represent weak to moderate pedogenic maturity indicating short stratigraphic breaks with rapid loess deposition. Micromorphological observations of thin sections suggested that clay illuviation and CaCO3 accumulation have operated within the paleosol profiles. CaCO3 features are often associated with clay coatings suggesting decalcification of carbonates followed by clay illuviation. Pedogenic CaCO3 probably resulted from the precipitation of the soil solution near the average depth of wetting front. The pedogenic CaCO3, illuvial clay, mottles, iron manganese features, pedal microstructure and blocky aggregates reveal variation in the pedogenic maturity among and within the loess–paleosol sections. The morphological (both micro- and macro-morphological) attributes of loess–paleosols suggest variation of climatic conditions during the Late Quaternary period in the Karewa Basin of Kashmir Valley, India.

Late-Holocene land surface change in a coupled social–ecological system, southern Iceland: a cross-scale tephrochronology approach

The chronological challenge of cross-scale analysis within coupled socio-ecological systems can be met with tephrochronology based on numerous well-dated tephra layers. We illustrate this with an enhanced chronology from Skaftártunga, south Iceland that is based on 200 stratigraphic profiles and 2635 individual tephra deposits from 23 different eruptions within the last 1140 years. We present new sediment-accumulation rate based dating of tephra layers from Grímsvötn in AD 1432 ± 5 and AD 1457 ± 5. These and other tephras underpin an analysis of land surface stability across multiple scales. The aggregate regional sediment accumulation records suggest a relatively slow rate of land surface change which can be explained by climate and land use change over the period of human occupation of the island (after AD ∼870), but the spatial patterning of change shows that it is more complex, with landscape scale hysteresis and path dependency making the relationship between climate and land surface instability contingent. An alternative steady state of much higher rates of sediment accumulation is seen in areas below 300 m asl after AD ∼870 despite large variations in climate, with two phases of increased erosion, one related to vegetation change (AD 870–1206) and another related to climate (AD 1597–1918). In areas above 300 m asl there is a short lived increase in erosion and related deposition after settlement (AD ∼870–935) and then relatively little additional change to present. Spatial correlation between rates of sediment accumulation at different profiles decreases rapidly after AD ∼935 from ∼4 km to less than 250 m as the landscape becomes more heterogeneous. These new insights are only possible using high-resolution tephrochronology applied spatially across a landscape, an approach that can be applied to the large areas of the Earth's surface affected by the repeated fallout of cm-scale tephra layers.

Multiphysics modeling of CO2 sequestration in a faulted saline formation in Italy

The present work describes the results of a modeling study addressing the geological sequestration of carbon dioxide (CO2) in an offshore multi-compartment reservoir located in Italy. The study is part of a large scale project aimed at implementing carbon capture and storage (CCS) technology in a power plant in Italy within the framework of the European Energy Programme for Recovery (EEPR). The processes modeled include multiphase flow and geomechanical effects occurring in the storage formation and the sealing layers, along with near wellbore effects, fault/thrust reactivation and land surface stability, for a CO2 injection rate of 1×106ton/a. Based on an accurate reproduction of the three-dimensional geological setting of the selected structure, two scenarios are discussed depending on a different distribution of the petrophysical properties of the formation used for injection, namely porosity and permeability. The numerical results help clarify the importance of: (i) facies models at the reservoir scale, properly conditioned on wellbore logs, in assessing the CO2 storage capacity; (ii) coupled wellbore-reservoir flow in allocating injection fluxes among permeable levels; and (iii) geomechanical processes, especially shear failure, in constraining the sustainable pressure buildup of a faulted reservoir.

Climate change and geomorphological hazards in the eastern European Alps

Climate and environmental changes associated with anthropogenic global warming are being increasingly identified in the European Alps, as seen by changes in long-term high-alpine temperature, precipitation, glacier cover and permafrost. In turn, these changes impact on land-surface stability, and lead to increased frequency and magnitude of natural mountain hazards, including rock falls, debris flows, landslides, avalanches and floods. These hazards also impact on infrastructure, and socio-economic and cultural activities in mountain regions. This paper presents two case studies (2003 heatwave, 2005 floods) that demonstrate some of the interlinkages between physical processes and human activity in climatically sensitive alpine regions that are responding to ongoing climate change. Based on this evidence, we outline future implications of climate change on mountain environments and its impact on hazards and hazard management in paraglacial mountain systems.

Comparisons and Interpretations of Charcoal and Organic Matter Radiocarbon Ages from Buried Soils in North-Central Colorado, USA

The reliability of radiocarbon ages based on soil organic matter (SOM) from Holocene buried soils in Middle Park, Colorado, is assessed by comparison with ages of charcoal. On average,14C ages of SOM from buried surface horizons are 880 ± 23014C yr younger than charcoal ages from the same horizon. Humic acid (HA) and low-temperature (400 °) combustion residue (LT) fractions are 390 ± 230 and 1290 ± 23014C yr younger than charcoal ages, respectively, and HA ages are on average 860 ± 14014C yr older than LT fractions. We interpret the offsets between14C ages of charcoal and SOM fractions and the consistent offsets between the HA and LT fractions to reflect the duration of pedogenesis and different residence times of the SOM fractions examined here. The stratigraphic coherence of charcoal14C ages suggests short residence time on the landscape, with little subsequent reworking.14C ages of HA and LT fractions are complimentary to charcoal, and HA ages are interpreted to represent minimum ages for the onset of pedogenesis and LT ages are considered maximum ages for burial. The14C chronology from buried soils indicates an episode of hillslope erosion in Middle Park during the early Holocene, followed by a long period of land surface stability and soil formation between 9000–4500 BP. Two episodes of late Holocene hillslope erosion between 3500–2500 and 1000–500 BP correspond with warming recognized in the Colorado Front Range, while surface stability and soil formation between 2500–1000 BP is contemporaneous with evidence for cooling at higher elevations.

Late Quaternary eolian dust in surficial deposits of a Colorado Plateau grassland: Controls on distribution and ecologic effects

In a semi-arid, upland setting on the Colorado Plateau that is underlain by nutrient-poor Paleozoic eolian sandstone, alternating episodes of dune activity and soil formation during the late Pleistocene and Holocene have produced dominantly sandy deposits that support grass and shrub communities. These deposits also contain eolian dust, especially in paleosols. Eolian dust in these deposits is indicated by several mineralogic and chemical disparities with local bedrock, but it is most readily shown by the abundance of titaniferous magnetite in the sandy deposits that is absent in local bedrock. Magnetite and some potential plant nutrients (especially, P, K, Na, Mn, and Zn) covary positively with depth (3–4 m) in dune-crest and dune-swale settings. Magnetite abundance also correlates strongly and positively with abundances of other elements (e.g., Ti, Li, As, Th, La, and Sc) that are geochemically stable in these environments. Soil-property variations with depth can be ascribed to three primary factors: (1) shifts in local geomorphic setting; (2) accumulation of relatively high amounts of atmospheric mineral dust inputs during periods of land-surface stability; and (3) variations in dust flux and composition that are likely related to changes in dust-source regions. Shifts in geomorphic setting are revealed by large variations in soil texture and are also expressed by changes in soil chemical and magnetic properties. Variable dust inputs are indicated by both changes in dust flux and changes in relations among magnetic, chemical, and textural properties. The largest of these changes is found in sediment that spans late Pleistocene to early Holocene time. Increased dust inputs to the central Colorado Plateau during this period may have been related to desiccation and shrinkage of large lakes from about 12 to 8 ka in western North America that exposed vast surfaces capable of emitting dust. Soil properties that result from variable dust accumulation and redistribution in these surficial deposits during the late Quaternary are important to modern ecosystem dynamics because some plants today utilize nutrients deposited as long ago as about 12–15 ky and because variations in fine-grained (silt) sediment, including eolian dust, influence soil-moisture capacity.

Pedostratigraphy and Carbonate Accumulation in the Last Interglacial Pedocomplex of the Chinese Loess Plateau

This paper examines the geographic variations of carbonate concentrations in last interglacial pedocomplex (S1) profiles along a northwest (NW)–southeast (SE) transect across the Chinese Loess Plateau. The average S1 carbonate concentration is the same as that of overlying loess (L1) and underlying loess (L2) at the northwesternmost site (Lanzhou), but variations in carbonate concentration within S1 pedocomplex are greater than the within‐loess (L1 and L2) variations, indicating that the carbonate translocation within the S1 pedocomplex had occurred. Carbonate was leached to greater depths to form more pronounced peaks in the three paleosols (S1S1, S1S2, S1S3) within the S1 pedocomplex at the Dingxi section. Farther SE to the Qinan section, the three paleosols (S1S1, S1S2, S1S3) have more distinguishable carbonate leaching and accumulation zones than at the Dingxi section. The S1 carbonate concentration at the Tianshui section suggests that the three paleosols were partially welded, as evidenced by the S1S3 and S1S2 paleosols sharing a major portion of the paleosol profile. Soil‐forming events occurred repeatedly in a single paleosol profile and the Ck horizon might have served as the carbonate accumulation zone for all three paleosols (S1S1, S1S2, S1S3) at the southeasternmost site (Lantian). Land surface stability complicated carbonate concentration processes in loessial paleosols and extra caution should be observed when interpreting climate implication of carbonate concentration data.

Late Holocene dune accretion and episodes of persistent drought in the Great Plains of Northeastern Colorado

The Great Plains of the Mid West USA contain dunefields which display stratigraphic evidence of episodic sand drift throughout the Holocene and, in some cases, the Late Pleistocene. Widespread aeolian activity has been linked to persistent megadroughts caused by a weakening of the tropical moisture-laden circulation from the Gulf of Mexico and equatorial Pacific. Infrared stimulated luminescence (IRSL) dating has been applied to two exposures in the Fort Morgan dunefield of northeastern Colorado where radiocarbon-dated buried soils provide ages for land surface stability. IRSL ages show that sand drift occurred episodically during the Late Holocene at 4.85, 2.37, 1.06, 0.80, 0.6–0.53 and 0.37 ka.

Holocene coastal dune development on the South Erradale peninsula, Wester Ross, Scotland

Synopsis Radiocarbon dates from peats within and below coastal dune sands at Opinan and Redpoint, Wester Ross, Scotland, provide age constraints on phases of peat accumulation, dune development, and podzolic soil formation. Although the two dune systems are only 4 km apart they do not share identical histories of landsurface stability and aeolian sand deposition. Most dune building occurred as relative sea level (RSL) was falling but because the dunes are perched on glacifluvial terraces several metres above RSL maximum, the creation of accommodation space consequent upon RSL fall was not a prerequisite for dune development. Some dune phases also correspond in timing with documented climate shifts to cooler, wetter and/or stormier conditions - in the Little Ice Age 400 cal. years bp , around 2500 cal. years bp , and at about 8100 cal. years bp . Preliminary estimates of the rate of podzolic soil development are similar to those reported for aeolian sandy parent materials elsewhere.

Deep weathering through time in central and northwestern Europe: problems of dating and interpretation of geological record

Upland and shield areas of central and northwestern Europe are characterised by an abundance of relict weathering mantles (saprolites). These saprolites, if accurately dated and interpreted, may serve as an important complementary source of information about long-term environmental history. In this paper, methods used to establish ages of weathering mantles are reviewed, such as stratigraphic and morphostratigraphic dating, clay mineral and stable isotope analysis, K–Ar and cosmogenic isotope dating, particularly with reference to European examples. The record of deep weathering in the Mesozoic and Cainozoic is examined to explain the peculiarities of the evidence and controls on the changing style of weathering through time. Weathering has been a continuous process through time, but general and local geological conditions have resulted in different ages of preserved mantles. An apparent trend from an earlier kaolinitic/ferrallitic style of weathering in the Mesozoic and Early Tertiary, towards a grussic style by the end of the Cainozoic, does not only reflect climate change, but it is also broadly consistent with tectonic/geomorphic history and related changes in land surface stability. Miocene and Plio–Pleistocene saprolites, in particular, show that in different geomorphological and lithological circumstances, different types of weathering mantles could have evolved.

Formation of a rhizogenic calcrete during a glacial stage(Oxygen Isotope Stage 12): its palaeoenvironmental stratigraphic significance

The morphology and micromorphology of a carbonate-cemented horizon within Anglian Stage, Oxygen Isotope Stage (OIS) 12, glaciofluvial outwash deposits at Leet Hill, southern Norfolk are characteristic of a rhizogenic calcrete. The horizon consists of a laterally continuous calcified root mat and an associated vertical rhizolith, both of which contain micro-fabrics typical of biologically precipitated carbonate, i.e. needle fibre calcite, calcified root cells and pelleted micrite. Formation of this calcrete is suggested to relate to the coincident occurrence of a phase of land surface stability and a period of climatic amelioration within the Anglian Stage during which permafrost decayed, a near-surface water table formed and a vegetation cover became established. The period of calcrete formation is tentatively correlated with other evidence for a climatic amelioration during the Anglian Stage in eastern England. The stratigraphic position of the calcrete suggests that this amelioration occurred after the Scandinavian ice had advanced into East Anglia but prior to the overriding of the region by the British ice mass. The discovery of this calcrete represents the first known description of a rhizogenic calcrete from a glacial stage. It presents the possibility that other, previously unstudied, carbonate horizons within Quaternary deposits of northwest Europe may in fact be calcretes and that these may provide further palaeoenvironmental and stratigraphic information.

Pedogenic modification of loess: significance for palaeoclimatic reconstructions

This review considers the role of pedogenic processes in modifying wind-blown dust (loess), concentrating particularly on the ways that resulting properties may be interpreted as indicators of past climatic conditions and changes. Emphasis is placed on the sequences of palaeosols developed within loess deposits that are frequently regarded as some of the best terrestrial equivalents of marine-sediment records of long-term global climatic change. A palaeosol is generally interpreted in terms of the broad pedogenic processes and environments assumed to be currently responsible for that type of soil forming at the present surface. Even the very presence of a palaeosol may have palaeoclimatic significance, however, in that it is often taken to indicate a period of relative land surface stability and warmer and/or moister conditions between cold and/or arid phases of loess accumulation. In reality, it may be more useful to consider many loess–palaeosol sequences in terms of changing balances between pedogenesis and loess accumulation over geological time. In most regions, it seems that the balance swings towards pedogenesis during interglacials or interstadials when sediment supply and transport are limited and the climate is warmer and/or wetter. Where accumulation rates are still appreciable during these ‘soil-forming intervals’, however, the soils and palaeosols may be accretionary with surface build-up keeping pace with pedogenesis. Welding may also occur where covering sediments are insufficiently thick to isolate an underlying palaeosol from the effects of pedogenesis active at a new land surface. Further complications occur due to reworking of palaeosols and syndepositional pedogenic alteration of loess units. Generally, such pedocomplexes can only be deciphered if the different pedogenic, geomorphic and sedimentary processes are identified and ordered within a pedosedimentary reconstruction. A recent trend has been to treat some loess–palaeosol sequences as quasi-continuous time series, particularly when comparing depth functions of climatic-proxy properties such as magnetic susceptibility and grain size with marine and ice-core isotope curves.

Succession of Alpine Vegetation in Relation to Environmental Changes around Tyndall Glacier on Mt. Kenya

Leopard's remains were discovered at Tyndall Glacier on Mt. Kenya in 1997. The radiocarbon dates of ca. 900 ± 100 yrs BP correspond to the shift from a warm period to a cool period and the age of the Tyndall Moraine. The leopard was probably not exposed from the ice of the Tyndall Glacier judging from the condition of the remains. The discovery of the leopard's remains in 1997 is consistent with the climatic change from a cool period which continued until the 19th century to warm period in the 20 century.The succession of alpine vegetation around Tyndall Glacier can be clarified from the conditions of glacial margins and moraines (Lewis Moraine : ca. 100 yrs BP, Tyndall Moraine : ca. 900-500 yrs BP). The Tyndall Glacier on Mt. Kenya retreated at a steady rate from the late 1950 s to 1996. The first colonist species over the new till, Senecio keniophytum, advanced at a rate similar to the retreat of the glacier. The species growing near the ice-front of Tyndall Glacier colonized in tandem with the retreat of the glacier. Till age and stability of land surface are important environmental factors controlling the vegetation pattern around Tyndall Glacier. The pioneer species make humus which results in an improved soil condition. About 70 to 100 yrs elapse from the glacial release before such large woody plants as Senecio keniodendron and Lobelia telekii grow on the glacier foreland.

Pleistocene paleosols in Norway: implications for past climate and glacial erosion

As recently as 7 years ago Quaternary geologists believed that there were no Pleistocene paleosols represented by non-peaty soil horizons (A, B, etc.) in Norway. However, several buried soils of this type have recently been reported and studied by stratigraphic, magnetic and chemical methods. Magnetic susceptibility is a useful method for identifying and correlating paleosols, even in areas of complex glacial stratigraphy such as the Nordic countries. At Sargejohka in Finnmark, up to seven different buried pedocomplexes are separated by tills and glaciotectonic deformation structures. They represent different periods of land surface stability and, with two possible exceptions, are not pseudosoils formed by a fluctuating groundwater table. The most important from stratigraphic and paleoclimatic points of view is a well-developed red–yellow paleosol numbered p3 counting down from the top. It is thought to be a podzol of the last interglacial. Later cryoturbation of pre-Mid Weichselian age has greatly altered its upper part, indicating a dramatic change in climate after development of the soil. At Lillehammer in southeastern Norway, remains of the oxidised zone of a buried paleosol, also thought to have formed mainly in the last interglacial, occur in an inferred Saalian till. The presence of buried Pleistocene paleosols in the interior of Norway (central part of the Fennoscandian glaciations) indicates that glacial erosion was locally less during several glacial cycles than previously thought.

Succession Processes of Alpine Vegetation in Response to Glacial Fluctuations of Tyndall Glacier, Mt. Kenya, Kenya

The Tyndall Glacier of Mt. Kenya retreated at a steady rate from the late 1950s to 1996. The first colonist species over the new till, Senecio keniophytum, advanced at a rate similar to the retreat of the glacier. The species growing near the ice-front of Tyndall Glacier colonize in tandem with retreat of the glacier. Till age and stability of land surface are important environmental factors controlling the vegetation pattern around Tyndall Glacier. Till age is affected by the glacial fluctuation. The stability of the land surface is governed by the particle-size of the surface material which is controlled by landform, geology, and past climatic conditions. The pioneer species make humus which results in improved soil condition. About 70 to 100 yr elapse from the glacial release for such large woody plants as Senecio keniodendron and Lobelia telekii to grow on the glacier foreland.

Succession Processes of Alpine Vegetation in Response to Glacial Fluctuations of Tyndall Glacier, Mt. Kenya, Kenya

The Tyndall Glacier of Mt. Kenya retreated at a steady rate from the late 1950s to 1996. The first colonist species over the new till, Senecio keniophytum, advanced at a rate similar to the retreat of the glacier. The species growing near the ice-front of Tyndall Glacier colonize in tandem with retreat of the glacier. Till age and stability of land surface are important environmental factors controlling the vegetation pattern around Tyndall Glacier. Till age is affected by the glacial fluctuation. The stability of the land surface is governed by the particle-size of the surface material which is controlled by landform, geology, and past climatic conditions. The pioneer species make humus which results in improved soil condition. About 70 to 100 yr elapse from the glacial release for such large woody plants as Senecio keniodendron and Lobelia telekii to grow on the glacier foreland.

How can the treatment of pedostratigraphic units in the North American stratigraphic code be improved?

Eolian sediments (sand, loess, and long-range-transported or aerosolic dust) are important archives of the Quaternary geologic and paleoclimatic record. They are extensive on the Earth's surface at all latitudes and can be dated using luminescence methods that require only the sediment itself. Unlike many Quaternary sediments, eolian deposits are direct indicators of atmospheric circulation. Furthermore, they are robust indicators of past aridity.Soils are naturally occurring bodies that mantle most of the land surface of Earth. Soil geography is a function of the combined effects of climate and vegetation, as well as parent material composition, parent material age, and topography. Because of their close links to climate, vegetation, and age of parent material, soils are powerful tools in Quaternary stratigraphy, geomorphology and landscape evolution, archeology, and paleoclimatology. Soils of the past, called paleosols, are particularly important in stratigraphy, interpreting past conditions of climate or vegetation, and the duration of land surface stability.