text: // Url
  var earthquakesURL = "https://earthquake.usgs.gov/earthquakes/feed/v1.0/summary/all_week.geojson"
  
  
  // Initialize & Create Two Separate LayerGroups: earthquakes 
  var earthquakes = new L.LayerGroup();
  
  // Define Variables for Tile Layers
  
  var grayscaleMap = L.tileLayer("https://api.mapbox.com/styles/v1/{id}/tiles/{z}/{x}/{y}?access_token={accessToken}", {
      attribution: "© <a href='https://www.mapbox.com/about/maps/'>Mapbox</a> © <a href='http://www.openstreetmap.org/copyright'>OpenStreetMap</a> <strong><a href='https://www.mapbox.com/map-feedback/' target='_blank'>Improve this map</a></strong>",
      tileSize: 512,
      maxZoom: 18,
      zoomOffset: -1,
      id: "mapbox/streets-v11",
      accessToken: API_KEY
    });
  
  
  
  // Define a baseMaps object to hold our base layers
  var baseMaps = {
      "Grayscale": grayscaleMap
  };
  
  // Create Overlay Object to Hold Overlay Layers
  var overlayMaps = {
      "Earthquakes": earthquakes,
  };
  
  // Create our map, giving it the streetmap and earthquakes layers to display on load
  var myMap = L.map("map", {
      center: [37.09, -95.71],
      zoom: 2,
      layers: [grayscaleMap, earthquakes]
  });
  
  // Create a layer control
    // Pass in our baseMaps and overlayMaps
    // Add the layer control to the map
  L.control.layers(baseMaps, overlayMaps).addTo(myMap);
  
  // GeoJSON Data with D3
  d3.json(earthquakesURL, function(data) {
      console.log(data)
      // Function to Determine Size of Marker Based on the Magnitude of the Earthquake
      function markerSize(magnitude) {
          if (magnitude === 0) {
            return 1;
          }
          return magnitude * 3;
      }
      // Function to Determine Style of Marker Based on the Magnitude of the Earthquake
      function circle(feature) {
          return {
            opacity: 1,
            fillOpacity: 1,
            fillColor: chooseColor(feature.properties.mag),
            color: "#000000",
            radius: markerSize(feature.properties.mag),
            stroke: true,
            weight: 0.5
          };
      }
      // Function to Determine Color of Marker Based on the Magnitude of the Earthquake
      function chooseColor(magnitude) {
          switch (true) {
          case magnitude > 5:
              return "#581845";
          case magnitude > 4:
              return "#900C3F";
          case magnitude > 3:
              return "#C70039";
          case magnitude > 2:
              return "#FF5733";
          case magnitude > 1:
              return "#FFC300";
          default:
              return "#DAF7A6";
          }
      }
      // Create a GeoJSON Layer Containing the Features Array on the Data Object
      L.geoJSON(data, {
          pointToLayer: function(feature, location) {
              return L.circleMarker(location);
          },
          style: circle,
          // Function to Run Once For Each feature in the features Array
          onEachFeature: function(feature, layer) {
              layer.bindPopup("<h4>Location: " + feature.properties.place + "</p><hr><p>Magnitude: " + feature.properties.mag + "</p>");
          }
      // Add Data to earthquakes LayerGroups 
      }).addTo(earthquakes);
      // Add earthquakes Layer to the Map
      earthquakes.addTo(myMap);
  });