This chapter reviews the present-day composition of the continental crust, the methods employed to derive these estimates, and the implications of the continental crust composition for the formation of the continents, Earth differentiation, and its geochemical inventories. We review the composition of the upper, middle, and lower continental crust. We then examine the bulk crust composition and the implications of this composition for crust generation and modification processes. Finally, we compare the Earth's crust with those of the other terrestrial planets in our solar system and speculate about what unique processes on Earth have given rise to this unusual crustal distribution.

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Composition of the Continental Crust

[1] The Shuttle Radar Topography Mission produced the most complete, highest-resolution digital elevation model of the Earth. The project was a joint endeavor of NASA, the National Geospatial-Intelligence Agency, and the German and Italian Space Agencies and flew in February 2000. It used dual radar antennas to acquire interferometric radar data, processed to digital topographic data at 1 arc sec resolution. Details of the development, flight operations, data processing, and products are provided for users of this revolutionary data set.

/pdf/the-shuttle-radar-topography-mission-4x49lt5xnj.pdf

The Shuttle Radar Topography Mission

Investigating soil moisture-climate interactions in a changing climate: A review

3.01 – Composition of the Continental Crust

[1] EGM2008 is a spherical harmonic model of the Earth's gravitational potential, developed by a least squares combination of the ITG-GRACE03S gravitational model and its associated error covariance matrix, with the gravitational information obtained from a global set of area-mean free-air gravity anomalies defined on a 5 arc-minute equiangular grid This grid was formed by merging terrestrial, altimetry-derived, and airborne gravity data Over areas where only lower resolution gravity data were available, their spectral content was supplemented with gravitational information implied by the topography EGM2008 is complete to degree and order 2159, and contains additional coefficients up to degree 2190 and order 2159 Over areas covered with high quality gravity data, the discrepancies between EGM2008 geoid undulations and independent GPS/Leveling values are on the order of ±5 to ±10 cm EGM2008 vertical deflections over USA and Australia are within ±11 to ±13 arc-seconds of independent astrogeodetic values These results indicate that EGM2008 performs comparably with contemporary detailed regional geoid models EGM2008 performs equally well with other GRACE-based gravitational models in orbit computations Over EGM96, EGM2008 represents improvement by a factor of six in resolution, and by factors of three to six in accuracy, depending on gravitational quantity and geographic area EGM2008 represents a milestone and a new paradigm in global gravity field modeling, by demonstrating for the first time ever, that given accurate and detailed gravimetric data, asingle global model may satisfy the requirements of a very wide range of applications

https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2011JB008916

The development and evaluation of the Earth Gravitational Model 2008 (EGM2008)

Modern radar altimetry challenges to Precise Orbit Determination

Time-variable Gravity Solutions from 1993 to 2013 from SLR and DORIS data

The first reliable model of the structure of the crust and upper mantle of Mars from remote observations was produced using data from the Mars Orbiter Laser Altimeter (MOLA) and the Radio Science investigation of Mars Global Surveyor (MGS). That model assumed a uniform crustal density and solved for the global variations in crustal thickness using a gravity field derived from preliminary MGS tracking. In that study, spherical harmonic potential coefficients were derived to degree and order 80, but crustal structure was interpreted cautiously to degree 60, or 360 km wavelength, owing to the presence of noise. Tracking normal equations have since been generated to degree 75, to degree 80 (supplemented by altimetric crossovers), and recently to degree 90, using new constants for the orientation of the spin pole and the rotation rate of Mars provided by the IAU2000 rotation model. Gravity models now incorporate tracking data coverage from the Primary and Extended MGS missions and the early phases of the Mars Odyssey mission. In the present study we exploit these advances in gravity modeling to present a refined crustal inversion, which we also interpret in the context of Mars' internal structure and thermal evolution.

An Improved Model of the Crustal Structure of Mars

. A spherical harmonic model of the lunar gravity field complete todegree and order 70 has been developed from S band Doppler tracking data fromthe Clementine mission, as well as historical tracking data from Lunar Orbiters1-5 and the Apollo 15 and 16 subsatellites. The model combines 361,000 Dopplerobservations from Clementinewith 347,000 historical observations. The historicaldata consist of mostly 60-s Doppler with a noise of 0.25 to several mm/s. TheClementine data consist of mostly 10-s Doppler data, with a data noise of 0.25mm/s for the observations from the Deep Space Network, and 2.5 mm/s for thedata from a naval tracking station at Pomonkey, Maryland. Observations providedClementine, provide the strongest satellite constraint on the Moon's low-degreefield. In contrast the historical data, collected by spacecraft that had lower periapsisaltitudes, provide distributed regions of high-resolution coverage within +29 ° ofthe nearside lunar equator. To obtain the solution for a high-degree field in the_bsence of a uniform distribution of observations, we applied an a priori power lawconstraint of the form 15 × lO-S/l 2 which had the effect of limiting the gravitationalpower and noise at short wavelengths. Coefficients through degree and order 18 arenot significantly affected by the constraint, and so the model permits geophysicalanalysis of effects of the major basins at degrees 10-12. The GLGM-2 modelconfirms major features of the lunar gravity field shown in previous gravitationalfield models but also reveals significantly more detail, particularly at intermediatewavelengths (103 kin). Free-air gravity anomaly maps derived from the new modelshow the nearside and farside highlands to be gravitationally smooth, reflecting astate of isostatic compensation. Mascon basins (including Imbrium, Serenitatis,Crisium, Smythii, and Humorum) are denoted by gravity highs first recognizedfrom Lunar Orbiter tracking. All of the major mascons are bounded by annuliof negative anomalies representing significant subsurface mass deficiencies. MareOrientale appears as a minor mascon surrounded by a horseshoe-shaped gravitylow centered on the Inner and Outer Rook rings that is evidence of significantsubsurface structural heterogeneity. Although direct tracking is not available over ,a significant part of the lunar farside, GLGM-2 resolves negative anomalies thatcorrelate with many farside basins, including South Pole-Aitken, Hertzsprung,Korolev, Moscoviense, Tsiolkovsky, and Freundlich-Sharonov.IntroductionUntil the launch of Clementine, on January 24, 1994,the sources of tracking data for gravity models derivedby U.S. investigators have been the Lunar Orbiters andthe Apollo spacecraft. The Lunar Orbiters were in-

from Clementine and other tracking data

We investigate the time-variable gravity changes in Europe retrieved from the initial GRACE monthly solutions spanning a 18 month duration from April 2002 to October 2003. Gravity anomaly maps are retrieved in Central Europe from the monthly satellite solutions we compare the fields according to various truncation levels (typically between degree 10 and 20) of the initial fields (expressed in spherical harmonics to degree 120). For these different degrees, an empirical orthogonal function (EOF) decomposition of the time-variable gravity field leads us to its main spatial and temporal characteristics. We show that the dominant signal is found to be annual with an amplitude and a phase both in agreement with predictions in Europe modeled using snow and soil-moisture variations from recent hydrology models. We compare these GRACE gravity field changes to surface gravity observations from 6 superconducting gravimeters of the GGP (Global Geodynamics Project) European sub-network, with a special attention to loading corrections. Initial results suggest that all 3 data sets (GRACE, hydrology and GGP) are responding to annual changes in near-surface water in Europe of a few microGal (at length scales of approx.1000 km) that show a high value in winter and a summer minimum. We also point out that the GRACE gravity field evolution seems to indicate that there is a trend in gravity between summer 2002 and summer 2003 which can be related to the 2003 heatwave in Europe and its hydrological consequences (drought). Despite the limited time span of our analysis and the uncertainties in retrieving a regional solution from the network of gravimeters, the calibration and validation aspects of the GRACE data processing based on the annual hydrology cycle in Europe are in progress.

Time Changes of the European Gravity Field from GRACE: A Comparison with Ground Measurements from Superconducting Gravimeters and with Hydrology Model Predictions

Frank G. Lemoine

Papers

Modern radar altimetry challenges to Precise Orbit Determination

Time-variable Gravity Solutions from 1993 to 2013 from SLR and DORIS data

An Improved Model of the Crustal Structure of Mars

from Clementine and other tracking data

Time Changes of the European Gravity Field from GRACE: A Comparison with Ground Measurements from Superconducting Gravimeters and with Hydrology Model Predictions