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Immersive visualization at the National Laboratory for Advanced Scientific Visualization (LAVIS) of a numerical simulation with a seamount that belongs to the Cocos Plate, Mexico. See the related paper in this issue; photograph courtesy of the author: Marina Manea.

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North panoramic view of the Citlaltépetl (Pico de Orizaba) volcano. The volcanic edifice shows some irregularities on its flanks, which represent the remnants of the ancient cones on both flanks, on which the present cone was built. This is the highest North American volcano (5685 m a.s.l.), still active with the only glacier preserved in Mexico. See the related article in this issue; photograph courtesy of the author: Gerardo Carrasco-Núñez.

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Comparison of the humerus distal end of two bears: a fossil Agriotherium and a recent Ursus Maritimus. On left, Agriotherium (MPGJ 5676) from Juchipila basin, Zacatecas Mexico, early-late Hemphillian age; the medial epicondyle is convex, the external epicondylar ridge has a thick rim with two deep grooves in the middle. On right, Ursus maritimus with a long hook-shaped medial condyle important in retaining prey for feeding. The lateral epicondylar ridge is concave deep throughout its length. See the related paper by Carranza-Castañeda and Wang in this issue.

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Lahar in the Montegrande ravine, Volcán de Colima, real-time monitoring image from station of the Centro de Geociencias de la Universidad Nacional Autónoma de México, date 2018-10-03, GMT 23:53:55. See the related article by Martínez-Valdés et al. in this issue.

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Longitudinal thin section of the new coral species Rayaphyllia atheca, holotype IGM 9204. 1, from the San Juan Raya Formation (Lower Cretaceous), Puebla, Mexico. Scale bar = 1 mm. See related article by Hannes Löser in this issue.

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Intermediate-depth seismicity in southern Mexico. The orange symbols represent earthquakes with depths between 50 and 10 km, while the yellow ones are earthquakes with depths greater than 100 km. In this area, hypocentral depths never exceed 300 km. Also, notice that in the westernmost part of the map, the seismicity no longer follows the pattern of being perpendicular to the trench. See related article by Guzmán-Speziale in the special section of this issue.

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Stalagmites collapsed by an earthquake in the San Jerónimo underground river, inside the Cacahuamilpa Grottoes, Taxco, Guerrero, Mexico. At the center of the photograph is Dr. Víctor Hugo Garduño-Monroy, in whose memory the third and last part of the Special Section “The Geology of Michoacán” is published in this issue.

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Clastic deposits covering volcanic deposits of the Aguajito Caldera, Baja California Sur, Mexico. Víctor Hugo Garduño-Monroy at the center of the image.

Special Section guest editors:

Isabel Israde-Alcántara and José Luis Macías

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View of a trench performed on the Jarácuaro paleo island, south west margin of Patzcuaro lake, showing lacustrine sediments (diatomites and clays) interlayered with volcanic deposits. Different deformation phases are recorded as result of phenomena of  uplifting and landslides of volcanic edifices as well of active faulting associate with the E-W regional fault system. This image justify the importance of the studies carried out by Víctor Hugo Garduño Monroy (on the right) to understand this factors in the lacustrine basin evolution and paleoenvironmental reconstruction in Mexico. To the left, Miguel Rodríguez Pascua.

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Valle de las Morrenas, Costa Rica. Valle de las Morrenas is a sequence of glacial lakes embedded in extensive till deposits due to the relative glacier movements during the Last Glacial Maximum. Credits: Leonardo Quesada, Néstor Veas, and Adolfo Quesada.

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Detailed view of a bryozoan in oblique section; in this specimen a large amount of the zooecia (elongated purple pores) are filled with calcite cement. This organisms were part of a diverse reef community in the Olinalá Formation (late Permian). Microphotograph taken with polarized light and analized with 1/4 lambda quartz wedge. Horizontal axis 2.5 mm. Courtesy of Edgar Juárez Arriaga

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View of the Popocatépetl volcano from the northwest. To the right of the crater you can see the Ventorrillo hill and the head of the Nexpayantla ravine. The front of the photo shows the Tlamacas dome, on which the station of the same name is located. See related article by Zaragoza et al. in this number; photo courtesy of the authors.

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Cupidito exposed as a transgressive unit at the south limb of Los Muertos anticline in the emblematic locality of La Huasteca, Nuevo Leon. Peritidal carbonates from the Cupido Formation, organized in subvertical strata, represent a marine regression that developed a sequence boundary marked by a collapse breccia (central vertical wall). See Torres de la Cruz et al. in this issue.

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Chevron folds, Albian-Cenomanian secession of Tamaulipas formation (competent and incompetent layers) on the Zimapán Basin, near San Juaquín, Querétaro. See related article of Vásquez Serrano et al. in this issue.

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Microphotography of a gomphoterium cranium bone from Tepeticpac, Tlaxcala, observed in cross-polarized light. The morphology of the bone is observed: osetons and osteocite lacunae are seen as well as reabsorption of the bone visible in Haversian canals that have lost their oval shape. Photograph by Luisa Strualino and Sergey Sedov. See related article by Straulino et al. in this issue.

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Apatite crystals [Ca5(PO)4(F,Cl,OH)] from the Chiapas massif complex samples selected for U-Pb analysis using LA-ICPMS technique. These crystals were selected because their size and they are free of inclusions or fractures. See related article by Ortega-Obregón in this issue.

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Domino structure in a inverse shear zone with tectonic transport to the NE. The beds are psamites from the Caracol Formation (Late Cretaceous). The outcrop is located in Pinos, Zacatecas, Mexico (UTM 14Q 2469669 N; 232315E). Photography: Ana Suárez Arias and Alberto Vásquez Serrano.

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Sequence of red beds formed by the fine-grained, largely lacustrine facies of the Late Eocene Yolomécatl Formation, placed near Santiago Yolomécatl, northwestern Oaxaca State, Mexico. See related article by Ferrusquía-Villafranca et al. in this issue.

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Affected strata with deformation structures generated by co-seismic activity of M≥5, in San Pedro El Alto, Acambay graben. Load-flame structures formed by liquefaction of silt, which is introduced into the upper layers. Pseudonodules formed by density difference between volcanic ash and sand. (Intensity VII on ESI 2007 scale). See related article by Velázquez-Bucio y Garduño-Monroy in this issue.

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Fulgurite Zacatecas. Fragments of skeletal crystals of Fe-silicate and two prismatic crystals (< 10 μ m) of Si-Fe (silicides) whiting the vitreous matrix. Scanning electron microcopy image; see related paper of Reyes-Salas et al. in this issue.