Fieldwork and geologic heritage

Name three classic instruments used by field geologists and briefly explain what each is used for.

List at least five minimum pieces of information that you must record in your notebook when describing an outcrop.

Field sketches are still used even though we all carry a camera on our cell phones. Explain what an interpreted drawing — selection of features, scale, annotations — provides that a photograph does not record by itself.

Describe how to take and label a rock sample correctly in the field, and explain why a sample without a reference to its collection point loses almost all its scientific value.

What are a hand lens and a steel scratch point used for in the field when describing a rock? Relate these observations to the mineral identification that will be carried out later in the lab.

Why is it advisable to sample fresh rock, removing the weathered rind, and to take several samples from the same level? Relate this practice to the reliability of subsequent laboratory analyses.

The diagram represents in plan view the measurement that a geologist has taken on inclined sandstone strata: "strike N $45^\circ$ E, dip $30^\circ$ SE".

1. a) Explain what each of the two values that make up this measurement means (strike and dip).

1. b) Identify which element of the diagram (the blue line or the orange arrow) represents each one, and justify your answer based on its orientation relative to north.

A student writes "dip 60° SW" in their notebook but forgets the strike of the stratum. Explain why the measurement remains incomplete and which two notations for the direction (azimuth and quadrants) they could have used.

The strike and dip measurements taken in the field end up represented on the geologic map. Explain how one goes from the notebook annotations to drawing the contacts and the structural symbols on the map, and why it is advisable to review them the same day.

GPS and cell phones have been incorporated into fieldwork. Explain two specific advantages they offer over traditional methods.

Name four basic safety and behavior rules for a geological field trip, related to equipment, weather, respect for property and the conservation of geosites.

Explain how a map is oriented in the field with the help of a compass and two known points on the terrain, and why this is the first operation on arriving at a work station.

On a forested mountain slope with thick soil cover, there are no continuous rock outcrops. You must accurately locate the stratigraphic contact between a lower formation of impermeable Paleozoic slates and an overlying horizontal formation of permeable Mesozoic limestones. While hiking up the slope, you record the following data:

• Elevation 700 m: Dark clayey soil with angular, shiny clasts of slaty rock; gentle slope (12°); oak forest.

• Elevation 840 m: The slope steepens abruptly to 38°; a horizontal line of springs and waterlogged areas with hygrophilic vegetation (rushes and mosses) appears.

• Elevation 870 m: Shallow soil with grayish limestone scree that reacts with 10% HCl; xerophilic scrub vegetation.

1. a) Deduce and interpret at approximately what elevation the lithological contact is located, justifying your deduction based on the observed hydrogeological behavior, geomorphological landforms, and botany.
2. b) If at the contact elevation you were to find a breccia with angular fragments of both rocks cemented by iron oxides, along with striations (slickensides) on the block walls, reason whether the contact is still a stratigraphic unconformity or if it has been reactivated as a fault.
3. c) Explain how you would represent this contact on the geological map according to official cartographic standards (observed contact vs. inferred or concealed contact), and justify which surface geophysical method (electrical resistivity tomography or seismic refraction) would allow you to verify its depth beneath the colluvial mantle without drilling boreholes.

During the mapping of the flank of a fold in fluvial sandstones, three students measure the dip of the same rock stratum at points separated by only 3 meters from each other, obtaining discordant values: Student A: 27° to the E; Student B: 48° to the E; Student C: 34° to the E.

Upon reviewing the field notes, it is verified that:

• Student A placed the clinometer on the inclined surface of an internal lamina of trough cross-bedding.

• Student B rested the compass on an open decompression joint plane at the edge of the scarp.

• Student C used the notebook as an auxiliary plane resting on the flat base of the stratum containing basal load casts, measuring along the line of maximum slope (perpendicular to the strike).

1. a) Diagnose the validity of the data from A and B: explain the conceptual error of each and why their measurements do not represent the tectonic dip of the formation.
2. b) A fourth student proposes calculating the arithmetic mean of the three measurements: $(27° + 48° + 34°)/3 = 36.3°$ to record it on the map. Rebut this proposal, justifying why averaging structural data without geological discrimination distorts the geometry of the mapping.
3. c) Describe with technical precision the standardized cartographic symbol that must be drawn on the map to reflect the correct measurement of student C (strike N000°E and dip 34°E), detailing the orientation of its strokes and the numerical value.

Following an episode of torrential rains (130 mm in 24 h), a slope movement is triggered in a river valley through which a hiking trail runs. Upon inspecting the terrain, you observe:

• A semicircular main scarp with a 2.5 m displacement at the head, with tension cracks open in the ground up to 20 m uphill from the scarp.

• Leaning pine trunks with curvature at their base ("pistol-butt trees") along the entire affected slope.

• At the base, a disorganized mass of waterlogged Miocene gypsiferous clays invading the riverbed, reducing its natural channel by half.

1. a) Identify the kinematic typology of the movement (rotational slide, translational slide, or mudflow) and deduce, based on botanical and geomorphological evidence, whether it is a completely new phenomenon or the reactivation of a pre-existing unstable mass.
2. b) The city council proposes bringing in heavy machinery immediately to excavate and remove the earth from the toe of the landslide and reopen the trail. Predict the geotechnical impact of this action on the overall stability of the slope and reason what will happen to the cracks at the head.
3. c) Design a stepped action plan in three phases (urgent safety intervention, corrective drainage/stabilization measures, and monitoring or surveillance system) that the technical report must fulfill before permitting pedestrian traffic.

What is geodiversity? Give two examples of geological heritage features that deserve protection.

What is a geopark? State how it differs from a national park and what aims it pursues in terms of conservation, education and local development.

Two volcanic outcrops in the same district are competing for a limited budget allocation for their designation and development as a Geosite (Geological Site of Interest):

• Site A: A morphologically well-preserved Strombolian cone, but composed of lapilli deposits that are very common in the region, located next to a paved state road and 2 km from a high school. It is at risk of anthropogenic degradation due to ongoing plundering of volcanic bombs.

• Site B: A highly eroded, exhumed phonolitic plug whose original relief has been dismantled, but which contains peridotite xenoliths from the upper mantle that are unique in the peninsular geological record. It is located in a rugged area that requires a two-hour hike on foot across steep terrain.

1. a) Evaluate and compare the scientific value versus the educational and outreach potential of both sites.
2. b) Knowing that the methodological criteria of the Spanish Geological Survey (IGME) weight representativeness, rarity, vulnerability, and accessibility, justify in a reasoned manner which of the two sites should be prioritized as a Geosite if the primary objective is to prevent the irreparable loss of unique geological heritage.
3. c) Design a conservation and management measure for the selected site that mitigates its primary risk factor without hindering scientific research.

A city council proposes opening a quarry on a hillside where dinosaur footprints (fossil tracks) outcrop. Argue why this action would damage geological heritage and propose an alternative compatible with economic activity.

An outdoor fossil footprint site is deteriorating due to weathering and visitors. Propose three protection measures compatible with visiting it and one prior documentation measure (casts or three-dimensional scanning), justifying them.

On a limestone slope dipping at 35°, a surface with bipedal and quadrupedal dinosaur tracks has been discovered on a bed of marly limestone that is highly friable and vulnerable to freeze-thaw weathering. The local city council proposes opening the site to the public without restrictions, allowing tourists to walk on the bed to take plaster casts and anchoring metal walkways directly onto the fossiliferous rock using drilled bolts.

1. a) Critically evaluate the municipal project: identify two physical and chemical degradation processes that this design would accelerate and justify the irreversibility of the damage to the footprints.
2. b) The paleontological study finds that the sauropod trackways show well-preserved mud expulsion rims (cushions) oriented N-S, while fossil wave ripple marks and desiccation cracks are perpendicularly superimposed on them. Interpret the evolution of the sedimentary environment and explain how you would translate this temporal sequence into accessible language for an interpretive field panel.
3. c) Design an alternative in situ intervention and museum display plan that balances educational display with the strict preservation of the bed, specifying access infrastructure, climate protection, and monitoring.