Comparison of volcanic features of Elysium (Mars) and Tibesti (Earth) MICHAEL C. MALIN* Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125 ABSTRACT the Tharsis region, which represent the Emi Koussi (19.7°N, 18.5°E; Fig. 1), largest and most conspicuous examples of situated at the extreme southern portion of The Elysium volcanic province on Mars martian volcanism (McCauley and others, the volcanic region, ranges from 60 to 80 and the Tibesti volcanic province in Chad, 1972; Carr, 1973, 1974). Comparison with km across and consists of 2,000 m of vol- Africa, were studied using Mariner 9, terrestrial volcanoes, especially those on the canics resting on Paleozoic and Cretaceous Landsat and Apollo photography. Elysium island of Hawaii, has been most fruitful sandstones which have been uplifted 1,500 Mons on Mars and Emi Koussi on Earth (Greeley, 1973). m. The original cone may have reached as show remarkable similarities in summit In this paper, another martian volcanic much as 4,000 m above sea level but is now caldera and flank morphologies. Each has a province will be studied. The Elysium re- only 3,415 m high, with a large (15-km), large central caldera —12 km in diameter gion has several structures which are not multiple-crater caldera some 500 m deep at and from 500 to 1,000 m deep; both cal- found elsewhere on Mars, as well as some the summit. Much of the volcanism oc- deras contain numerous craters and large, which are similar to those of Tharsis. Com- curred during the middle and late Tertiary, irregular pits. Channel-like features which parison will be made with terrestrial fea- with only limited activity during the head at the calderas and taper downslope tures of the Tibesti region of northern Holocene. Current activity is restricted to a show evidence of collapse and possible lava Chad, Africa, which displays a variety of few fumaroles near the southern base of the erosion. Elysium Mons rises some 14 ± 1.5 volcanic forms similar to those of Elysium. volcano. Most of the erosional dissection of km above its base, and the summit is about After establishing the regional setting of the volcano's flanks (Fig. 1) occurred dur- 20 km above the 6.1-mbar mean martian the volcanic fields, two volcanoes, Emi ing the early Pleistocene. pressure surface. Crater size/frequency Koussi on Earth and Elysium Mons on The Tibesti region has experienced ex- analysis indicates most of the craters are of Mars, will be compared in detail. Three tensive tectonic and erosional activity. endogenic origin. The subdued, hummocky main topics will then be addressed: (1) evi- Where present, Paleozoic (Cambro-Or- terrain on the flanks are distinctly different dence for silicic volcanism on Mars, (2) the dovician) sandstones rest unconform- from the slopes of the younger Tharsis tectonic situation of volcanoes situated on ably on an eroded Precambrian surface Ridge volcanoes, showing little if any sign stable (that is, nonmoving) crust, and (3) and dip away from the uplifted massif. of recent material flow. the evidence against fluvial erosion in the Paleozoic formations are in general totally The lack of aqueous erosional forms on relatively recent past on Mars. missing north of the east-west branch and Elysium Mons argues strongly against re- immediately west of the lower portion of cent (~ 105 to 106 yr) pluvial episodes. The REGIONAL SETTING the north-south branch of the province, forms and associations of features through- OF TIBESTI (EARTH) the result of post-Carboniferous, pre- out the Elysium region suggest that central Cretaceous warping, uplift, and subse- volcanism started earlier in Elysium than in Several reports (Geze and others, 1959; quent erosion. Prior to the Lutetian (lower Tharsis and that the source of the Elysium Vincent, 1960, 1970) have presented de- Eocene), the massif was cut by northeast- volcanics has been chemically evolved, with tailed descriptions and interpretations of and north-northeast-trending faults which evidence of silicic magma. Finally, the data the Tibesti region of northern Chad, Africa. follow Precambrian trends. Subsequent up- are consistent with the view that the mar- In this section, only a brief review of some lift along a north-northwest axis was fol- tian crust has been stable and essentially of their results will be presented. lowed by the overall tilting of the entire motionless for an extended period of mar- The Tibesti volcanic province occupies block toward the north-northeast. Sig- tian geologic time. approximately one-third of a triangular up- nificant erosion then occurred, forming land region some 100,000 km2 in area, ap- much of the present topographic relief and INTRODUCTION proximately 1,100 km south of the establishing the drainage system still Mediterranean Sea and 2,000 km west of preserved throughout most of the area The discovery of large volcanoes on the the Red Sea. The highest point is Emi (Geze and others, 1959; Vincent, 1960, planet Mars was one of the most important Koussi at 3,415 m; numerous areas are 1970; Hagedorn, 1971). This erosion has and exciting results of the Mariner 9 mis- more than 2,000 m high. been placed roughly at the boundary be- sion (Masursky and others, 1972; Most volcanoes in Tibesti exhibit two tween the Pliocene and Pleistocene. McCauley and others, 1972; Masursky, distinctive characteristics: wide, low-slope, The volcanism is believed to have started 1973). Much attention has been focused on shield-like profiles and large, central cal- during the very early Tertiary with the ex- Olympus Mons and the other volcanoes of deras (s 10-km diam). Unlike Hawaii, in trusion of basalts and andesites in floods of some places the Tibesti shields appear to be probable fissural origin. This phase was fol- " Present address: Planetology and Oceanography Section, Jet Propulsion Laboratory, Pasadena, Califor- formed of an ignimbritic mass covering lowed by the initial formation of large, cen- nia 91103. older volcanics. tral volcanoes through the emission of a se- Geological Society of America Bulletin, v. 88, p. 908-919, 7 figs., July 1977, Doc. no. 70702. 908 Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/88/7/908/3429828/i0016-7606-88-7-908.pdf by guest on 28 September 2021 COMPARISON OF VOLCANIC FEATURES: ELYSIUM (MARS) AND TIBESTI (EARTH) 909 Figure 1. Landsat photograph: Emi Koussi and surroundings, Earth. Earth Resources Technology Satellite (Landsat) multispectral scanner photograph of southeastern Tibesti showing Emi Koussi in lower right. Volcano is about 70 km in diameter with 12 x 15 km caldera. Recent basalts appear very dark in this infrared photograph. Massive valley incision occurred at the beginning of the Pleistocene. Portions of the Yega, Oyoye, Toon, and Tieroko vol- canoes can be seen in the upper left section of the image. For photographic support data, see Table 1. quence of trachyandesites, trachyphono- basaltic flows on the slopes of, and within dera), and the deposition of the sodium lites, and some rhyolites and of essentially the old valleys around, the caldera. Vol- carbonates within these craters occurred tholeiitic basalts — labradorite-rich, canic activity within the province has con- during the Holocene (Quaternary), and olivine-poor porphyries with abundant tinued throughout the Quaternary primar- fumarolic activity is still present throughout magnetite and ilmenite. Several of the ig- ily in the form of a hybrid volcanism in the the province. nimbrite sheets postdate the erosion of the west [potassic trachyandesites preceding older shields but are older than the massive fluid doreites (an olivine-bearing sub- REGIONAL SETTING valley incision which occurred at the begin- alkaline trachyandesite) and andesites] and OF ELYSIUM (MARS) ning of the Pleistocene. The deposition of in the east by the formation of a second ignimbrites at Koussi was apparently as- caldera at Koussi. The explosions which The Elysium Planitia is dominated by a sociated with the collapse formation of the formed the craters Trau au natron and Era group of three volcanoes located near caldera and was followed by a period of Kohor (the latter within the Koussi cal- 210°W long between 18° and 32°N lat (Fig. Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/88/7/908/3429828/i0016-7606-88-7-908.pdf by guest on 28 September 2021 910 M. C. MALIN 2). The region consists of a broad, elliptical TABLE 1. PHOTOGRAPHIC DATA dome (2,400 x 1,700 km, major axis north-northeast), similar to the Tharsis Spacecraft Frame Lat Long Picture Picture Sun ele- Negative Ridge, with the three volcanoes occupying height width vation generation (km) (km) angle the triangular summit. The crest of this broad dome would lie approximately 6 km Apollo 7 5-1621 (1) 19.92°N 18.54°E 120 150 14° 5 above the mean martian pressure surface, Landsat 1 were it not for the presence of the large vol- RBV 1010-08425-1 (1) 20.18°N 18.20°E 185 185 31° 4 canic constructs. MSS 1064-08425-6 (1) 20.15°N 18.25°E 185 185 36° 4 The northernmost volcano, Hecates f 32° Tholus, is about 180 km in diameter. It is a Mariner 9 6391738 (9, ) 21.90°N 213.90°W 439 897 3 8982649 29.43°N 221.09°W 565 721 32° flat-topped, dome-like volcano with rela- 9054539 (2) 29.50°N 211.67°W 561 718 32° tively steep slopes that are convex in profile. 9126429 29.70°N 202.46°W 560 719 33° A UVS altimetry scan which, fortuitously, 7651453 (3,*) 24.54°N 216.94°W 528 684 27° traced across the dome showed its height to 7651593 (3) 23.58°N 204.95°W 632 732 17° be about 6 km (Hord and others, 1974).